x264源代码简单分析 x264命令行工具（x264 exe）
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H.264源代码分析文章列表：
【编码 - x264】
x264源代码简单分析：概述
x264源代码简单分析：x264命令行工具（x264.exe）
x264源代码简单分析：编码器主干部分-1
x264源代码简单分析：编码器主干部分-2
x264源代码简单分析：x264_slice_write()
x264源代码简单分析：滤波（Filter）部分
x264源代码简单分析：宏块分析（Analysis）部分-帧内宏块（Intra）
x264源代码简单分析：宏块分析（Analysis）部分-帧间宏块（Inter）
x264源代码简单分析：宏块编码（Encode）部分
x264源代码简单分析：熵编码（Entropy Encoding）部分
FFmpeg与libx264接口源代码简单分析
【解码 - libavcodec H.264 解码器】
FFmpeg的H.264解码器源代码简单分析：概述
FFmpeg的H.264解码器源代码简单分析：解析器（Parser）部分
FFmpeg的H.264解码器源代码简单分析：解码器主干部分
FFmpeg的H.264解码器源代码简单分析：熵解码（EntropyDecoding）部分
FFmpeg的H.264解码器源代码简单分析：宏块解码（Decode）部分-帧内宏块（Intra）
FFmpeg的H.264解码器源代码简单分析：宏块解码（Decode）部分-帧间宏块（Inter）
FFmpeg的H.264解码器源代码简单分析：环路滤波（Loop Filter）部分
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本文简单分析x264项目中的命令行工具（x264.exe）的源代码。该命令行工具可以调用libx264将YUV格式像素数据编码为H.264码流。
函数调用关系图
X264命令行工具的源代码在x264中的位置如下图所示。
单击查看更清晰的图片
X264命令行工具的源代码的调用关系如下图所示。
单击查看更清晰的图片
从图中可以看出，X264命令行工具调用了libx264的几个API完成了H.264编码工作。使用libx264的API进行编码可以参考《 最简单的视频编码器：基于libx264（编码YUV为H.264）》，这个流程中最关键的API包括：
x264_param_default()：设置参数集结构体x264_param_t的缺省值。
x264_encoder_open()：打开编码器。
x264_encoder_headers()：输出SPS，PPS，SEI等信息。
x264_encoder_encode()：编码输出一帧图像。
x264_encoder_close()：关闭编码器。
在X264命令行工具中，main()首先调用parse()解析输入的命令行参数，然后调用encode()进行编码。parse()首先调用x264_param_default()为存储参数的结构体x264_param_t赋默认值；然后在一个大循环中调用getopt_long()逐个解析输入的参数，并作相应的处理；最后调用select_input()和select_output()解析输入文件格式（例如yuv，y4m…）和输出文件格式（例如raw，flv，MP4…）。encode()首先调用x264_encoder_open()打开H.264编码器，然后调用x264_encoder_headers()输出H.264码流的头信息（例如SPS、PPS、SEI），接着进入一个循环并且调用encode_frame()逐帧编码视频，最后调用x264_encoder_close()关闭解码器。其中encode_frame()中又调用了x264_encoder_encode()完成了具体的编码工作。下文将会对上述流程展开分析。
main()
main()是x264控制台程序的入口函数，定义如下所示。//主函数int main( int argc, char **argv ){ //参数集 x264_param_t param; cli_opt_t opt = {0}; int ret = 0; FAIL_IF_ERROR( x264_threading_init(), "unable to initialize threading\n" )#ifdef _WIN32 FAIL_IF_ERROR( !get_argv_utf8( &argc, &argv ), "unable to convert command line to UTF-8\n" ) GetConsoleTitleW( org_console_title, CONSOLE_TITLE_SIZE ); _setmode( _fileno( stdin ), _O_BINARY ); _setmode( _fileno( stdout ), _O_BINARY ); _setmode( _fileno( stderr ), _O_BINARY );#endif /* Parse command line */ //解析命令行输入 if( parse( argc, argv, ¶m, &opt ) < 0 ) ret = -1;#ifdef _WIN32 /* Restore title; it can be changed by input modules */ SetConsoleTitleW( org_console_title );#endif /* Control-C handler */ signal( SIGINT, sigint_handler ); //编码 if( !ret ) ret = encode( ¶m, &opt ); /* clean up handles */ if( filter.free ) filter.free( opt.hin ); else if( opt.hin ) cli_input.close_file( opt.hin ); if( opt.hout ) cli_output.close_file( opt.hout, 0, 0 ); if( opt.tcfile_out ) fclose( opt.tcfile_out ); if( opt.qpfile ) fclose( opt.qpfile );#ifdef _WIN32 SetConsoleTitleW( org_console_title ); free( argv );#endif return ret;}可以看出main()的定义很简单，它主要调用了两个函数：parse()和encode()。main()首先调用parse()解析输入的命令行参数，然后调用encode()进行编码。下面分别分析这两个函数。
parse()
parse()用于解析命令行输入的参数（存储于argv[]中）。它的定义如下所示。//解析命令行输入static int parse( int argc, char **argv, x264_param_t *param, cli_opt_t *opt ){ char *input_filename = NULL; const char *demuxer = demuxer_names[0]; char *output_filename = NULL; const char *muxer = muxer_names[0]; char *tcfile_name = NULL; x264_param_t defaults; char *profile = NULL; char *vid_filters = NULL; int b_thread_input = 0; int b_turbo = 1; int b_user_ref = 0; int b_user_fps = 0; int b_user_interlaced = 0; cli_input_opt_t input_opt; cli_output_opt_t output_opt; char *preset = NULL; char *tune = NULL; //初始化参数默认值 x264_param_default( &defaults ); cli_log_level = defaults.i_log_level; memset( &input_opt, 0, sizeof(cli_input_opt_t) ); memset( &output_opt, 0, sizeof(cli_output_opt_t) ); input_opt.bit_depth = 8; input_opt.input_range = input_opt.output_range = param->vui.b_fullrange = RANGE_AUTO; int output_csp = defaults.i_csp; opt->b_progress = 1; /* Presets are applied before all other options. */ for( optind = 0;; ) { int c = getopt_long( argc, argv, short_options, long_options, NULL ); if( c == -1 ) break; if( c == OPT_PRESET ) preset = optarg; if( c == OPT_TUNE ) tune = optarg; else if( c == '?' ) return -1; } if( preset && !strcasecmp( preset, "placebo" ) ) b_turbo = 0; //设置preset，tune if( x264_param_default_preset( param, preset, tune ) < 0 ) return -1; /* Parse command line options */ //解析命令行选项 for( optind = 0;; ) { int b_error = 0; int long_options_index = -1; int c = getopt_long( argc, argv, short_options, long_options, &long_options_index ); if( c == -1 ) { break; } //不同的选项做不同的处理 switch( c ) { case 'h': help( &defaults, 0 );//"-h"帮助菜单 exit(0); case OPT_LONGHELP: help( &defaults, 1 ); exit(0); case OPT_FULLHELP: help( &defaults, 2 ); exit(0); case 'V': print_version_info();//打印版本信息 exit(0); case OPT_FRAMES: param->i_frame_total = X264_MAX( atoi( optarg ), 0 ); break; case OPT_SEEK: opt->i_seek = X264_MAX( atoi( optarg ), 0 ); break; case 'o': output_filename = optarg;//输出文件路径 break; case OPT_MUXER: FAIL_IF_ERROR( parse_enum_name( optarg, muxer_names, &muxer ), "Unknown muxer `%s'\n", optarg ) break; case OPT_DEMUXER: FAIL_IF_ERROR( parse_enum_name( optarg, demuxer_names, &demuxer ), "Unknown demuxer `%s'\n", optarg ) break; case OPT_INDEX: input_opt.index_file = optarg; break; case OPT_QPFILE: opt->qpfile = x264_fopen( optarg, "rb" ); FAIL_IF_ERROR( !opt->qpfile, "can't open qpfile `%s'\n", optarg ) if( !x264_is_regular_file( opt->qpfile ) ) { x264_cli_log( "x264", X264_LOG_ERROR, "qpfile incompatible with non-regular file `%s'\n", optarg ); fclose( opt->qpfile ); return -1; } break; case OPT_THREAD_INPUT: b_thread_input = 1; break; case OPT_QUIET: cli_log_level = param->i_log_level = X264_LOG_NONE;//设置log级别 break; case 'v': cli_log_level = param->i_log_level = X264_LOG_DEBUG;//设置log级别 break; case OPT_LOG_LEVEL: if( !parse_enum_value( optarg, log_level_names, &cli_log_level ) ) cli_log_level += X264_LOG_NONE; else cli_log_level = atoi( optarg ); param->i_log_level = cli_log_level;//设置log级别 break; case OPT_NOPROGRESS: opt->b_progress = 0; break; case OPT_TUNE: case OPT_PRESET: break; case OPT_PROFILE: profile = optarg; break; case OPT_SLOWFIRSTPASS: b_turbo = 0; break; case 'r': b_user_ref = 1; goto generic_option; case OPT_FPS: b_user_fps = 1; param->b_vfr_input = 0; goto generic_option; case OPT_INTERLACED: b_user_interlaced = 1; goto generic_option; case OPT_TCFILE_IN: tcfile_name = optarg; break; case OPT_TCFILE_OUT: opt->tcfile_out = x264_fopen( optarg, "wb" ); FAIL_IF_ERROR( !opt->tcfile_out, "can't open `%s'\n", optarg ) break; case OPT_TIMEBASE: input_opt.timebase = optarg; break; case OPT_PULLDOWN: FAIL_IF_ERROR( parse_enum_value( optarg, pulldown_names, &opt->i_pulldown ), "Unknown pulldown `%s'\n", optarg ) break; case OPT_VIDEO_FILTER: vid_filters = optarg; break; case OPT_INPUT_FMT: input_opt.format = optarg;//输入文件格式 break; case OPT_INPUT_RES: input_opt.resolution = optarg;//输入分辨率 break; case OPT_INPUT_CSP: input_opt.colorspace = optarg;//输入色域 break; case OPT_INPUT_DEPTH: input_opt.bit_depth = atoi( optarg );//输入颜色位深 break; case OPT_DTS_COMPRESSION: output_opt.use_dts_compress = 1; break; case OPT_OUTPUT_CSP: FAIL_IF_ERROR( parse_enum_value( optarg, output_csp_names, &output_csp ), "Unknown output csp `%s'\n", optarg ) // correct the parsed value to the libx264 csp value#if X264_CHROMA_FORMAT static const uint8_t output_csp_fix[] = { X264_CHROMA_FORMAT, X264_CSP_RGB };#else static const uint8_t output_csp_fix[] = { X264_CSP_I420, X264_CSP_I422, X264_CSP_I444, X264_CSP_RGB };#endif param->i_csp = output_csp = output_csp_fix[output_csp]; break; case OPT_INPUT_RANGE: FAIL_IF_ERROR( parse_enum_value( optarg, range_names, &input_opt.input_range ), "Unknown input range `%s'\n", optarg ) input_opt.input_range += RANGE_AUTO; break; case OPT_RANGE: FAIL_IF_ERROR( parse_enum_value( optarg, range_names, ¶m->vui.b_fullrange ), "Unknown range `%s'\n", optarg ); input_opt.output_range = param->vui.b_fullrange += RANGE_AUTO; break; default:generic_option: { if( long_options_index < 0 ) { for( int i = 0; long_options[i].name; i++ ) if( long_options[i].val == c ) { long_options_index = i; break; } if( long_options_index < 0 ) { /* getopt_long already printed an error message */ return -1; } } //解析以字符串方式输入的参数 //即选项名称和选项值都是字符串 b_error |= x264_param_parse( param, long_options[long_options_index].name, optarg ); } } if( b_error ) { const char *name = long_options_index > 0 ? long_options[long_options_index].name : argv[optind-2]; x264_cli_log( "x264", X264_LOG_ERROR, "invalid argument: %s = %s\n", name, optarg ); return -1; } } /* If first pass mode is used, apply faster settings. */ if( b_turbo ) x264_param_apply_fastfirstpass( param ); /* Apply profile restrictions. */ //设置profile if( x264_param_apply_profile( param, profile ) < 0 ) return -1; /* Get the file name */ FAIL_IF_ERROR( optind > argc - 1 || !output_filename, "No %s file. Run x264 --help for a list of options.\n", optind > argc - 1 ? "input" : "output" ) //根据文件名的后缀确定输出的文件格式（raw H264，flv，mp4...） if( select_output( muxer, output_filename, param ) ) return -1; FAIL_IF_ERROR( cli_output.open_file( output_filename, &opt->hout, &output_opt ), "could not open output file `%s'\n", output_filename ) //输入文件路径 input_filename = argv[optind++]; video_info_t info = {0}; char demuxername[5]; /* set info flags to be overwritten by demuxer as necessary. */ //设置info结构体 info.csp = param->i_csp; info.fps_num = param->i_fps_num; info.fps_den = param->i_fps_den; info.fullrange = input_opt.input_range == RANGE_PC; info.interlaced = param->b_interlaced; if( param->vui.i_sar_width > 0 && param->vui.i_sar_height > 0 ) { info.sar_width = param->vui.i_sar_width; info.sar_height = param->vui.i_sar_height; } info.tff = param->b_tff; info.vfr = param->b_vfr_input; input_opt.seek = opt->i_seek; input_opt.progress = opt->b_progress; input_opt.output_csp = output_csp; //设置输入文件的格式（yuv，y4m...） if( select_input( demuxer, demuxername, input_filename, &opt->hin, &info, &input_opt ) ) return -1; FAIL_IF_ERROR( !opt->hin && cli_input.open_file( input_filename, &opt->hin, &info, &input_opt ), "could not open input file `%s'\n", input_filename ) x264_reduce_fraction( &info.sar_width, &info.sar_height ); x264_reduce_fraction( &info.fps_num, &info.fps_den ); x264_cli_log( demuxername, X264_LOG_INFO, "%dx%d%c %u:%u @ %u/%u fps (%cfr)\n", info.width, info.height, info.interlaced ? 'i' : 'p', info.sar_width, info.sar_height, info.fps_num, info.fps_den, info.vfr ? 'v' : 'c' ); if( tcfile_name ) { FAIL_IF_ERROR( b_user_fps, "--fps + --tcfile-in is incompatible.\n" ) FAIL_IF_ERROR( timecode_input.open_file( tcfile_name, &opt->hin, &info, &input_opt ), "timecode input failed\n" ) cli_input = timecode_input; } else FAIL_IF_ERROR( !info.vfr && input_opt.timebase, "--timebase is incompatible with cfr input\n" ) /* init threaded input while the information about the input video is unaltered by filtering */#if HAVE_THREAD if( info.thread_safe && (b_thread_input || param->i_threads > 1 || (param->i_threads == X264_THREADS_AUTO && x264_cpu_num_processors() > 1)) ) { if( thread_input.open_file( NULL, &opt->hin, &info, NULL ) ) { fprintf( stderr, "x264 [error]: threaded input failed\n" ); return -1; } cli_input = thread_input; }#endif /* override detected values by those specified by the user */ if( param->vui.i_sar_width > 0 && param->vui.i_sar_height > 0 ) { info.sar_width = param->vui.i_sar_width; info.sar_height = param->vui.i_sar_height; } if( b_user_fps ) { info.fps_num = param->i_fps_num; info.fps_den = param->i_fps_den; } if( !info.vfr ) { info.timebase_num = info.fps_den; info.timebase_den = info.fps_num; } if( !tcfile_name && input_opt.timebase ) { uint64_t i_user_timebase_num; uint64_t i_user_timebase_den; int ret = sscanf( input_opt.timebase, "%"SCNu64"/%"SCNu64, &i_user_timebase_num, &i_user_timebase_den ); FAIL_IF_ERROR( !ret, "invalid argument: timebase = %s\n", input_opt.timebase ) else if( ret == 1 ) { i_user_timebase_num = info.timebase_num; i_user_timebase_den = strtoul( input_opt.timebase, NULL, 10 ); } FAIL_IF_ERROR( i_user_timebase_num > UINT32_MAX || i_user_timebase_den > UINT32_MAX, "timebase you specified exceeds H.264 maximum\n" ) opt->timebase_convert_multiplier = ((double)i_user_timebase_den / info.timebase_den) * ((double)info.timebase_num / i_user_timebase_num); info.timebase_num = i_user_timebase_num; info.timebase_den = i_user_timebase_den; info.vfr = 1; } if( b_user_interlaced ) { info.interlaced = param->b_interlaced; info.tff = param->b_tff; } if( input_opt.input_range != RANGE_AUTO ) info.fullrange = input_opt.input_range; //初始化滤镜filter //filter可以认为是一种“扩展”了的输入源 if( init_vid_filters( vid_filters, &opt->hin, &info, param, output_csp ) ) return -1; /* set param flags from the post-filtered video */ param->b_vfr_input = info.vfr; param->i_fps_num = info.fps_num; param->i_fps_den = info.fps_den; param->i_timebase_num = info.timebase_num; param->i_timebase_den = info.timebase_den; param->vui.i_sar_width = info.sar_width; param->vui.i_sar_height = info.sar_height; info.num_frames = X264_MAX( info.num_frames - opt->i_seek, 0 ); if( (!info.num_frames || param->i_frame_total < info.num_frames) && param->i_frame_total > 0 ) info.num_frames = param->i_frame_total; param->i_frame_total = info.num_frames; if( !b_user_interlaced && info.interlaced ) {#if HAVE_INTERLACED x264_cli_log( "x264", X264_LOG_WARNING, "input appears to be interlaced, enabling %cff interlaced mode.\n" " If you want otherwise, use --no-interlaced or --%cff\n", info.tff ? 't' : 'b', info.tff ? 'b' : 't' ); param->b_interlaced = 1; param->b_tff = !!info.tff;#else x264_cli_log( "x264", X264_LOG_WARNING, "input appears to be interlaced, but not compiled with interlaced support\n" );#endif } /* if the user never specified the output range and the input is now rgb, default it to pc */ int csp = param->i_csp & X264_CSP_MASK; if( csp >= X264_CSP_BGR && csp <= X264_CSP_RGB ) { if( input_opt.output_range == RANGE_AUTO ) param->vui.b_fullrange = RANGE_PC; /* otherwise fail if they specified tv */ FAIL_IF_ERROR( !param->vui.b_fullrange, "RGB must be PC range" ) } /* Automatically reduce reference frame count to match the user's target level * if the user didn't explicitly set a reference frame count. */ if( !b_user_ref ) { int mbs = (((param->i_width)+15)>>4) * (((param->i_height)+15)>>4); for( int i = 0; x264_levels[i].level_idc != 0; i++ ) if( param->i_level_idc == x264_levels[i].level_idc ) { while( mbs * param->i_frame_reference > x264_levels[i].dpb && param->i_frame_reference > 1 ) param->i_frame_reference--; break; } } return 0;}下面简单梳理parse()的流程：
（1）调用x264_param_default()为存储参数的结构体x264_param_t赋默认值
（2）调用x264_param_default_preset()为x264_param_t赋值
（3）在一个大循环中调用getopt_long()逐个解析输入的参数，并作相应的处理。举几个例子：a)“-h”：调用help()打开帮助菜单。b)“-V”调用print_version_info()打印版本信息。c)对于长选项，调用x264_param_parse()进行处理。（4）调用select_input()解析输出文件格式（例如raw，flv，MP4…）
（5）调用select_output()解析输入文件格式（例如yuv，y4m…）
下文按照顺序记录parse()中涉及到的函数：
x264_param_default()
x264_param_default_preset()
help()
print_version_info()
x264_param_parse()
select_input()
select_output()
x264_param_default()
x264_param_default()是一个x264的API。该函数用于设置x264中x264_param_t结构体的默认值。函数的声明如下所示。/* x264_param_default: * fill x264_param_t with default values and do CPU detection */void x264_param_default( x264_param_t * );/**************************************************************************** * x264_param_default: ****************************************************************************///初始化参数默认值void x264_param_default( x264_param_t *param ){ /* */ memset( param, 0, sizeof( x264_param_t ) ); /* CPU autodetect */ param->cpu = x264_cpu_detect(); param->i_threads = X264_THREADS_AUTO; param->i_lookahead_threads = X264_THREADS_AUTO; param->b_deterministic = 1; param->i_sync_lookahead = X264_SYNC_LOOKAHEAD_AUTO; /* Video properties */ param->i_csp = X264_CHROMA_FORMAT ? X264_CHROMA_FORMAT : X264_CSP_I420; param->i_width = 0; param->i_height = 0; param->vui.i_sar_width = 0; param->vui.i_sar_height= 0; param->vui.i_overscan = 0; /* undef */ param->vui.i_vidformat = 5; /* undef */ param->vui.b_fullrange = -1; /* default depends on input */ param->vui.i_colorprim = 2; /* undef */ param->vui.i_transfer = 2; /* undef */ param->vui.i_colmatrix = -1; /* default depends on input */ param->vui.i_chroma_loc= 0; /* left center */ param->i_fps_num = 25; param->i_fps_den = 1; param->i_level_idc = -1; param->i_slice_max_size = 0; param->i_slice_max_mbs = 0; param->i_slice_count = 0; /* Encoder parameters */ //编码参数--最常见 param->i_frame_reference = 3; param->i_keyint_max = 250; param->i_keyint_min = X264_KEYINT_MIN_AUTO; param->i_bframe = 3; param->i_scenecut_threshold = 40; param->i_bframe_adaptive = X264_B_ADAPT_FAST; param->i_bframe_bias = 0; param->i_bframe_pyramid = X264_B_PYRAMID_NORMAL; param->b_interlaced = 0; param->b_constrained_intra = 0; param->b_deblocking_filter = 1; param->i_deblocking_filter_alphac0 = 0; param->i_deblocking_filter_beta = 0; param->b_cabac = 1; param->i_cabac_init_idc = 0; //码率控制模块 Rate Control param->rc.i_rc_method = X264_RC_CRF; param->rc.i_bitrate = 0; param->rc.f_rate_tolerance = 1.0; param->rc.i_vbv_max_bitrate = 0; param->rc.i_vbv_buffer_size = 0; param->rc.f_vbv_buffer_init = 0.9; param->rc.i_qp_constant = 23 + QP_BD_OFFSET; param->rc.f_rf_constant = 23; param->rc.i_qp_min = 0; param->rc.i_qp_max = QP_MAX; param->rc.i_qp_step = 4; param->rc.f_ip_factor = 1.4; param->rc.f_pb_factor = 1.3; param->rc.i_aq_mode = X264_AQ_VARIANCE; param->rc.f_aq_strength = 1.0; param->rc.i_lookahead = 40; param->rc.b_stat_write = 0; param->rc.psz_stat_out = "x264_2pass.log"; param->rc.b_stat_read = 0; param->rc.psz_stat_in = "x264_2pass.log"; param->rc.f_qcompress = 0.6; param->rc.f_qblur = 0.5; param->rc.f_complexity_blur = 20; param->rc.i_zones = 0; param->rc.b_mb_tree = 1; /* Log */ //日志模块 param->pf_log = x264_log_default; param->p_log_private = NULL; param->i_log_level = X264_LOG_INFO; /* */ //分析模块 Analysis param->analyse.intra = X264_ANALYSE_I4x4 | X264_ANALYSE_I8x8; param->analyse.inter = X264_ANALYSE_I4x4 | X264_ANALYSE_I8x8 | X264_ANALYSE_PSUB16x16 | X264_ANALYSE_BSUB16x16; param->analyse.i_direct_mv_pred = X264_DIRECT_PRED_SPATIAL; param->analyse.i_me_method = X264_ME_HEX; param->analyse.f_psy_rd = 1.0; param->analyse.b_psy = 1; param->analyse.f_psy_trellis = 0; param->analyse.i_me_range = 16; param->analyse.i_subpel_refine = 7; param->analyse.b_mixed_references = 1; param->analyse.b_chroma_me = 1; param->analyse.i_mv_range_thread = -1; param->analyse.i_mv_range = -1; // set from level_idc param->analyse.i_chroma_qp_offset = 0; param->analyse.b_fast_pskip = 1; param->analyse.b_weighted_bipred = 1; param->analyse.i_weighted_pred = X264_WEIGHTP_SMART; param->analyse.b_dct_decimate = 1; param->analyse.b_transform_8x8 = 1; param->analyse.i_trellis = 1; param->analyse.i_luma_deadzone[0] = 21; param->analyse.i_luma_deadzone[1] = 11; param->analyse.b_psnr = 0; param->analyse.b_ssim = 0; param->i_cqm_preset = X264_CQM_FLAT; memset( param->cqm_4iy, 16, sizeof( param->cqm_4iy ) ); memset( param->cqm_4py, 16, sizeof( param->cqm_4py ) ); memset( param->cqm_4ic, 16, sizeof( param->cqm_4ic ) ); memset( param->cqm_4pc, 16, sizeof( param->cqm_4pc ) ); memset( param->cqm_8iy, 16, sizeof( param->cqm_8iy ) ); memset( param->cqm_8py, 16, sizeof( param->cqm_8py ) ); memset( param->cqm_8ic, 16, sizeof( param->cqm_8ic ) ); memset( param->cqm_8pc, 16, sizeof( param->cqm_8pc ) ); param->b_repeat_headers = 1; param->b_annexb = 1; param->b_aud = 0; param->b_vfr_input = 1; param->i_nal_hrd = X264_NAL_HRD_NONE; param->b_tff = 1; param->b_pic_struct = 0; param->b_fake_interlaced = 0; param->i_frame_packing = -1; param->b_opencl = 0; param->i_opencl_device = 0; param->opencl_device_id = NULL; param->psz_clbin_file = NULL;}从源代码可以看出，x264_param_default()对输入的存储参数的结构体x264_param_t的成员变量进行了赋值工作。
x264_param_default_preset()
x264_param_default_preset()是一个libx264的API，用于设置x264的preset和tune。该函数的声明如下所示。/* Multiple tunings can be used if separated by a delimiter in ",./-+", * however multiple psy tunings cannot be used. * film, animation, grain, stillimage, psnr, and ssim are psy tunings. * * returns 0 on success, negative on failure (e.g. invalid preset/tune name). */int x264_param_default_preset( x264_param_t *, const char *preset, const char *tune );//设置preset，tuneint x264_param_default_preset( x264_param_t *param, const char *preset, const char *tune ){ x264_param_default( param ); //设置preset if( preset && x264_param_apply_preset( param, preset ) < 0 ) return -1; //设置tune if( tune && x264_param_apply_tune( param, tune ) < 0 ) return -1; return 0;}从源代码可以看出，x264_param_default_preset()调用x264_param_apply_preset()设置preset，调用x264_param_apply_tune()设置tune。记录一下这两个函数。
x264_param_apply_preset()
x264_param_apply_preset()用于设置preset。该函数的定义如下所示。
//设置presetstatic int x264_param_apply_preset( x264_param_t *param, const char *preset ){ char *end; int i = strtol( preset, &end, 10 ); if( *end == 0 && i >= 0 && i < sizeof(x264_preset_names)/sizeof(*x264_preset_names)-1 ) preset = x264_preset_names[i]; //几种不同的preset设置不同的参数 if( !strcasecmp( preset, "ultrafast" ) ) { param->i_frame_reference = 1; param->i_scenecut_threshold = 0; param->b_deblocking_filter = 0;//不使用去块滤波 param->b_cabac = 0;//不使用CABAC param->i_bframe = 0;//不使用B帧 param->analyse.intra = 0; param->analyse.inter = 0; param->analyse.b_transform_8x8 = 0;//不使用8x8DCT param->analyse.i_me_method = X264_ME_DIA;//运动搜索方法使用“Diamond” param->analyse.i_subpel_refine = 0; param->rc.i_aq_mode = 0; param->analyse.b_mixed_references = 0; param->analyse.i_trellis = 0; param->i_bframe_adaptive = X264_B_ADAPT_NONE; param->rc.b_mb_tree = 0; param->analyse.i_weighted_pred = X264_WEIGHTP_NONE;//不使用加权 param->analyse.b_weighted_bipred = 0; param->rc.i_lookahead = 0; } else if( !strcasecmp( preset, "superfast" ) ) { param->analyse.inter = X264_ANALYSE_I8x8|X264_ANALYSE_I4x4; param->analyse.i_me_method = X264_ME_DIA;//钻石模板 param->analyse.i_subpel_refine = 1;//亚像素运动估计质量为1 param->i_frame_reference = 1; param->analyse.b_mixed_references = 0; param->analyse.i_trellis = 0; param->rc.b_mb_tree = 0; param->analyse.i_weighted_pred = X264_WEIGHTP_SIMPLE; param->rc.i_lookahead = 0; } else if( !strcasecmp( preset, "veryfast" ) ) { param->analyse.i_me_method = X264_ME_HEX;//六边形模板 param->analyse.i_subpel_refine = 2; param->i_frame_reference = 1; param->analyse.b_mixed_references = 0; param->analyse.i_trellis = 0; param->analyse.i_weighted_pred = X264_WEIGHTP_SIMPLE; param->rc.i_lookahead = 10; } else if( !strcasecmp( preset, "faster" ) ) { param->analyse.b_mixed_references = 0; param->i_frame_reference = 2; param->analyse.i_subpel_refine = 4; param->analyse.i_weighted_pred = X264_WEIGHTP_SIMPLE; param->rc.i_lookahead = 20; } else if( !strcasecmp( preset, "fast" ) ) { param->i_frame_reference = 2; param->analyse.i_subpel_refine = 6; param->analyse.i_weighted_pred = X264_WEIGHTP_SIMPLE; param->rc.i_lookahead = 30; } else if( !strcasecmp( preset, "medium" ) ) { /* Default is medium */ } else if( !strcasecmp( preset, "slow" ) ) { param->analyse.i_me_method = X264_ME_UMH;//UMH相对复杂 param->analyse.i_subpel_refine = 8;//亚像素运动估计质量为8 param->i_frame_reference = 5; param->i_bframe_adaptive = X264_B_ADAPT_TRELLIS; param->analyse.i_direct_mv_pred = X264_DIRECT_PRED_AUTO; param->rc.i_lookahead = 50; } else if( !strcasecmp( preset, "slower" ) ) { param->analyse.i_me_method = X264_ME_UMH; param->analyse.i_subpel_refine = 9; param->i_frame_reference = 8; param->i_bframe_adaptive = X264_B_ADAPT_TRELLIS; param->analyse.i_direct_mv_pred = X264_DIRECT_PRED_AUTO; param->analyse.inter |= X264_ANALYSE_PSUB8x8; param->analyse.i_trellis = 2; param->rc.i_lookahead = 60; } else if( !strcasecmp( preset, "veryslow" ) ) { param->analyse.i_me_method = X264_ME_UMH; param->analyse.i_subpel_refine = 10; param->analyse.i_me_range = 24; param->i_frame_reference = 16; param->i_bframe_adaptive = X264_B_ADAPT_TRELLIS; param->analyse.i_direct_mv_pred = X264_DIRECT_PRED_AUTO; param->analyse.inter |= X264_ANALYSE_PSUB8x8; param->analyse.i_trellis = 2; param->i_bframe = 8; param->rc.i_lookahead = 60; } else if( !strcasecmp( preset, "placebo" ) ) { param->analyse.i_me_method = X264_ME_TESA;//TESA很慢 param->analyse.i_subpel_refine = 11; param->analyse.i_me_range = 24; param->i_frame_reference = 16; param->i_bframe_adaptive = X264_B_ADAPT_TRELLIS; param->analyse.i_direct_mv_pred = X264_DIRECT_PRED_AUTO; param->analyse.inter |= X264_ANALYSE_PSUB8x8; param->analyse.b_fast_pskip = 0; param->analyse.i_trellis = 2; param->i_bframe = 16; param->rc.i_lookahead = 60; } else { x264_log( NULL, X264_LOG_ERROR, "invalid preset '%s'\n", preset ); return -1; } return 0;}可以看出x264_param_apply_preset()通过strcasecmp()比较字符串的方法得到输入的preset类型；然后根据preset类型，设定 x264_param_t中相应的参数。
x264_param_apply_tune()
x264_param_apply_tune()用于设置tune。该函数的定义如下所示。
//设置tunestatic int x264_param_apply_tune( x264_param_t *param, const char *tune ){ char *tmp = x264_malloc( strlen( tune ) + 1 ); if( !tmp ) return -1; tmp = strcpy( tmp, tune ); //分解一个字符串为一个字符串数组。第2个参数为分隔符 char *s = strtok( tmp, ",./-+" ); int psy_tuning_used = 0; //设置 //这里是循环的，可以设置多次 while( s ) { if( !strncasecmp( s, "film", 4 ) ) { if( psy_tuning_used++ ) goto psy_failure; param->i_deblocking_filter_alphac0 = -1; param->i_deblocking_filter_beta = -1; param->analyse.f_psy_trellis = 0.15; } else if( !strncasecmp( s, "animation", 9 ) ) { if( psy_tuning_used++ ) goto psy_failure; param->i_frame_reference = param->i_frame_reference > 1 ? param->i_frame_reference*2 : 1; param->i_deblocking_filter_alphac0 = 1; param->i_deblocking_filter_beta = 1; param->analyse.f_psy_rd = 0.4; param->rc.f_aq_strength = 0.6; param->i_bframe += 2; } else if( !strncasecmp( s, "grain", 5 ) ) { if( psy_tuning_used++ ) goto psy_failure; param->i_deblocking_filter_alphac0 = -2; param->i_deblocking_filter_beta = -2; param->analyse.f_psy_trellis = 0.25; param->analyse.b_dct_decimate = 0; param->rc.f_pb_factor = 1.1; param->rc.f_ip_factor = 1.1; param->rc.f_aq_strength = 0.5; param->analyse.i_luma_deadzone[0] = 6; param->analyse.i_luma_deadzone[1] = 6; param->rc.f_qcompress = 0.8; } else if( !strncasecmp( s, "stillimage", 10 ) ) { if( psy_tuning_used++ ) goto psy_failure; param->i_deblocking_filter_alphac0 = -3; param->i_deblocking_filter_beta = -3; param->analyse.f_psy_rd = 2.0; param->analyse.f_psy_trellis = 0.7; param->rc.f_aq_strength = 1.2; } else if( !strncasecmp( s, "psnr", 4 ) ) { if( psy_tuning_used++ ) goto psy_failure; param->rc.i_aq_mode = X264_AQ_NONE; param->analyse.b_psy = 0; } else if( !strncasecmp( s, "ssim", 4 ) ) { if( psy_tuning_used++ ) goto psy_failure; param->rc.i_aq_mode = X264_AQ_AUTOVARIANCE; param->analyse.b_psy = 0; } else if( !strncasecmp( s, "fastdecode", 10 ) ) { param->b_deblocking_filter = 0; param->b_cabac = 0; param->analyse.b_weighted_bipred = 0; param->analyse.i_weighted_pred = X264_WEIGHTP_NONE; } else if( !strncasecmp( s, "zerolatency", 11 ) ) { //zerolatency速度快 param->rc.i_lookahead = 0; param->i_sync_lookahead = 0; param->i_bframe = 0;//不使用B帧 param->b_sliced_threads = 1; param->b_vfr_input = 0; param->rc.b_mb_tree = 0; } else if( !strncasecmp( s, "touhou", 6 ) ) { if( psy_tuning_used++ ) goto psy_failure; param->i_frame_reference = param->i_frame_reference > 1 ? param->i_frame_reference*2 : 1; param->i_deblocking_filter_alphac0 = -1; param->i_deblocking_filter_beta = -1; param->analyse.f_psy_trellis = 0.2; param->rc.f_aq_strength = 1.3; if( param->analyse.inter & X264_ANALYSE_PSUB16x16 ) param->analyse.inter |= X264_ANALYSE_PSUB8x8; } else { x264_log( NULL, X264_LOG_ERROR, "invalid tune '%s'\n", s ); x264_free( tmp ); return -1; } if( 0 ) { psy_failure: x264_log( NULL, X264_LOG_WARNING, "only 1 psy tuning can be used: ignoring tune %s\n", s ); } s = strtok( NULL, ",./-+" ); } x264_free( tmp ); return 0;}可以看出x264_param_apply_tune()首先通过strtok()得到存储tune[]数组；然后通过strncasecmp()比较字符串的方法判断当前的tune类型；最后根据tune类型，设定 x264_param_t中相应的参数。
help()
help()用于打印帮助菜单。在x264命令行程序中添加“-h”参数后会调用该函数。该函数的定义如下所示。//帮助菜单//longhelp标识是否展开更长的帮助菜单static void help( x264_param_t *defaults, int longhelp ){ char buf[50]; //H0(),H1(),H2()都是printf() //H1(),H2()只有“长帮助菜单”的情况下才会调用printf()#define H0 printf#define H1 if(longhelp>=1) printf#define H2 if(longhelp==2) printf H0( "x264 core:%d%s\n" "Syntax: x264 [options] -o outfile infile\n" "\n" "Infile can be raw (in which case resolution is required),\n" " or YUV4MPEG (*.y4m),\n" " or Avisynth if compiled with support (%s).\n" " or libav* formats if compiled with lavf support (%s) or ffms support (%s).\n" "Outfile type is selected by filename:\n" " .264 -> Raw bytestream\n" " .mkv -> Matroska\n" " .flv -> Flash Video\n" " .mp4 -> MP4 if compiled with GPAC or L-SMASH support (%s)\n" "Output bit depth: %d (configured at compile time)\n" "\n" "Options:\n" "\n" " -h, --help List basic options\n" " --longhelp List more options\n" " --fullhelp List all options\n" "\n", X264_BUILD, X264_VERSION,#if HAVE_AVS "yes",#else "no",#endif#if HAVE_LAVF "yes",#else "no",#endif#if HAVE_FFMS "yes",#else "no",#endif#if HAVE_GPAC "gpac",#elif HAVE_LSMASH "lsmash",#else "no",#endif x264_bit_depth ); H0( "Example usage:\n" ); H0( "\n" ); H0( " Constant quality mode:\n" ); H0( " x264 --crf 24 -o ); H0( "\n" ); H0( " Two-pass with a bitrate of 1000kbps:\n" ); H0( " x264 --pass 1 --bitrate 1000 -o ); H0( " x264 --pass 2 --bitrate 1000 -o ); H0( "\n" ); H0( " Lossless:\n" ); H0( " x264 --qp 0 -o ); H0( "\n" ); H0( " Maximum PSNR at the cost of speed and visual quality:\n" ); H0( " x264 --preset placebo --tune psnr -o ); H0( "\n" ); H0( " Constant bitrate at 1000kbps with a 2 second-buffer:\n"); H0( " x264 --vbv-bufsize 2000 --bitrate 1000 -o ); H0( "\n" ); H0( "Presets:\n" ); H0( "\n" ); H0( " --profile Force the limits of an H.264 profile\n" " Overrides all settings.\n" ); H2(#if X264_CHROMA_FORMAT <= X264_CSP_I420#if BIT_DEPTH==8 " - baseline:\n" " --no-8x8dct --bframes 0 --no-cabac\n" " --cqm flat --weightp 0\n" " No interlaced.\n" " No lossless.\n" " - main:\n" " --no-8x8dct --cqm flat\n" " No lossless.\n" " - high:\n" " No lossless.\n"#endif " - high10:\n" " No lossless.\n" " Support for bit depth 8-10.\n"#endif#if X264_CHROMA_FORMAT <= X264_CSP_I422 " - high422:\n" " No lossless.\n" " Support for bit depth 8-10.\n" " Support for 4:2:0/4:2:2 chroma subsampling.\n"#endif " - high444:\n" " Support for bit depth 8-10.\n" " Support for 4:2:0/4:2:2/4:4:4 chroma subsampling.\n" ); else H0( " - "#if X264_CHROMA_FORMAT <= X264_CSP_I420#if BIT_DEPTH==8 "baseline,main,high,"#endif "high10,"#endif#if X264_CHROMA_FORMAT <= X264_CSP_I422 "high422,"#endif "high444\n" ); H0( " --preset Use a preset to select encoding settings [medium]\n" " Overridden by user settings.\n" ); H2( " - ultrafast:\n" " --no-8x8dct --aq-mode 0 --b-adapt 0\n" " --bframes 0 --no-cabac --no-deblock\n" " --no-mbtree --me dia --no-mixed-refs\n" " --partitions none --rc-lookahead 0 --ref 1\n" " --scenecut 0 --subme 0 --trellis 0\n" " --no-weightb --weightp 0\n" " - superfast:\n" " --no-mbtree --me dia --no-mixed-refs\n" " --partitions i8x8,i4x4 --rc-lookahead 0\n" " --ref 1 --subme 1 --trellis 0 --weightp 1\n" " - veryfast:\n" " --no-mixed-refs --rc-lookahead 10\n" " --ref 1 --subme 2 --trellis 0 --weightp 1\n" " - faster:\n" " --no-mixed-refs --rc-lookahead 20\n" " --ref 2 --subme 4 --weightp 1\n" " - fast:\n" " --rc-lookahead 30 --ref 2 --subme 6\n" " --weightp 1\n" " - medium:\n" " Default settings apply.\n" " - slow:\n" " --b-adapt 2 --direct auto --me umh\n" " --rc-lookahead 50 --ref 5 --subme 8\n" " - slower:\n" " --b-adapt 2 --direct auto --me umh\n" " --partitions all --rc-lookahead 60\n" " --ref 8 --subme 9 --trellis 2\n" " - veryslow:\n" " --b-adapt 2 --bframes 8 --direct auto\n" " --me umh --merange 24 --partitions all\n" " --ref 16 --subme 10 --trellis 2\n" " --rc-lookahead 60\n" " - placebo:\n" " --bframes 16 --b-adapt 2 --direct auto\n" " --slow-firstpass --no-fast-pskip\n" " --me tesa --merange 24 --partitions all\n" " --rc-lookahead 60 --ref 16 --subme 11\n" " --trellis 2\n" ); else H0( " - ultrafast,superfast,veryfast,faster,fast\n" " - medium,slow,slower,veryslow,placebo\n" ); H0( " --tune Tune the settings for a particular type of source\n" " or situation\n" " Overridden by user settings.\n" " Multiple tunings are separated by commas.\n" " Only one psy tuning can be used at a time.\n" ); H2( " - film (psy tuning):\n" " --deblock -1:-1 --psy-rd :0.15\n" " - animation (psy tuning):\n" " --bframes {+2} --deblock 1:1\n" " --psy-rd 0.4: --aq-strength 0.6\n" " --ref {Double if >1 else 1}\n" " - grain (psy tuning):\n" " --aq-strength 0.5 --no-dct-decimate\n" " --deadzone-inter 6 --deadzone-intra 6\n" " --deblock -2:-2 --ipratio 1.1 \n" " --pbratio 1.1 --psy-rd :0.25\n" " --qcomp 0.8\n" " - stillimage (psy tuning):\n" " --aq-strength 1.2 --deblock -3:-3\n" " --psy-rd 2.0:0.7\n" " - psnr (psy tuning):\n" " --aq-mode 0 --no-psy\n" " - ssim (psy tuning):\n" " --aq-mode 2 --no-psy\n" " - fastdecode:\n" " --no-cabac --no-deblock --no-weightb\n" " --weightp 0\n" " - zerolatency:\n" " --bframes 0 --force-cfr --no-mbtree\n" " --sync-lookahead 0 --sliced-threads\n" " --rc-lookahead 0\n" ); else H0( " - psy tunings: film,animation,grain,\n" " stillimage,psnr,ssim\n" " - other tunings: fastdecode,zerolatency\n" ); H2( " --slow-firstpass Don't force these faster settings with --pass 1:\n" " --no-8x8dct --me dia --partitions none\n" " --ref 1 --subme {2 if >2 else unchanged}\n" " --trellis 0 --fast-pskip\n" ); else H1( " --slow-firstpass Don't force faster settings with --pass 1\n" ); H0( "\n" ); H0( "Frame-type options:\n" ); H0( "\n" ); H0( " -I, --keyint Maximum GOP size [%d]\n" , defaults->i_keyint_max ); H2( " -i, --min-keyint Minimum GOP size [auto]\n" ); H2( " --no-scenecut Disable adaptive I-frame decision\n" ); H2( " --scenecut How aggressively to insert extra I-frames [%d]\n" , defaults->i_scenecut_threshold ); H2( " --intra-refresh Use Periodic Intra Refresh instead of IDR frames\n" ); H1( " -b, --bframes Number of B-frames between I and P [%d]\n" , defaults->i_bframe ); H1( " --b-adapt Adaptive B-frame decision method [%d]\n" " Higher values may lower threading efficiency.\n" " - 0: Disabled\n" " - 1: Fast\n" " - 2: Optimal (slow with high --bframes)\n", defaults->i_bframe_adaptive ); H2( " --b-bias Influences how often B-frames are used [%d]\n" , defaults->i_bframe_bias ); H1( " --b-pyramid Keep some B-frames as references [%s]\n" " - none: Disabled\n" " - strict: Strictly hierarchical pyramid\n" " - normal: Non-strict (not Blu-ray compatible)\n", strtable_lookup( x264_b_pyramid_names, defaults->i_bframe_pyramid ) ); H1( " --open-gop Use recovery points to close GOPs\n" " Only available with b-frames\n" ); H1( " --no-cabac Disable CABAC\n" ); H1( " -r, --ref Number of reference frames [%d]\n" , defaults->i_frame_reference ); H1( " --no-deblock Disable loop filter\n" ); H1( " -f, --deblock Loop filter parameters [%d:%d]\n" , defaults->i_deblocking_filter_alphac0, defaults->i_deblocking_filter_beta ); H2( " --slices Number of slices per frame; forces rectangular\n" " slices and is overridden by other slicing options\n" ); else H1( " --slices Number of slices per frame\n" ); H2( " --slices-max Absolute maximum slices per frame; overrides\n" " slice-max-size/slice-max-mbs when necessary\n" ); H2( " --slice-max-size Limit the size of each slice in bytes\n" ); H2( " --slice-max-mbs Limit the size of each slice in macroblocks (max)\n" ); H2( " --slice-min-mbs Limit the size of each slice in macroblocks (min)\n" ); H0( " --tff Enable interlaced mode (top field first)\n" ); H0( " --bff Enable interlaced mode (bottom field first)\n" ); H2( " --constrained-intra Enable constrained intra prediction.\n" ); H0( " --pulldown Use soft pulldown to change frame rate\n" " - none, 22, 32, 64, double, triple, euro (requires cfr input)\n" ); H2( " --fake-interlaced Flag stream as interlaced but encode progressive.\n" " Makes it possible to encode 25p and 30p Blu-Ray\n" " streams. Ignored in interlaced mode.\n" ); H2( " --frame-packing For stereoscopic videos define frame arrangement\n" " - 0: checkerboard - pixels are alternatively from L and R\n" " - 1: column alternation - L and R are interlaced by column\n" " - 2: row alternation - L and R are interlaced by row\n" " - 3: side by side - L is on the left, R on the right\n" " - 4: top bottom - L is on top, R on bottom\n" " - 5: frame alternation - one view per frame\n" ); H0( "\n" ); H0( "Ratecontrol:\n" ); H0( "\n" ); H1( " -q, --qp Force constant QP (0-%d, 0=lossless)\n" , QP_MAX ); H0( " -B, --bitrate Set bitrate (kbit/s)\n" ); H0( " --crf Quality-based VBR (%d-51) [%.1f]\n" , 51 - QP_MAX_SPEC, defaults->rc.f_rf_constant ); H1( " --rc-lookahead Number of frames for frametype lookahead [%d]\n" , defaults->rc.i_lookahead ); H0( " --vbv-maxrate Max local bitrate (kbit/s) [%d]\n" , defaults->rc.i_vbv_max_bitrate ); H0( " --vbv-bufsize Set size of the VBV buffer (kbit) [%d]\n" , defaults->rc.i_vbv_buffer_size ); H2( " --vbv-init Initial VBV buffer occupancy [%.1f]\n" , defaults->rc.f_vbv_buffer_init ); H2( " --crf-max With CRF+VBV, limit RF to this value\n" " May cause VBV underflows!\n" ); H2( " --qpmin Set min QP [%d]\n" , defaults->rc.i_qp_min ); H2( " --qpmax Set max QP [%d]\n" , defaults->rc.i_qp_max ); H2( " --qpstep Set max QP step [%d]\n" , defaults->rc.i_qp_step ); H2( " --ratetol Tolerance of ABR ratecontrol and VBV [%.1f]\n" , defaults->rc.f_rate_tolerance ); H2( " --ipratio QP factor between I and P [%.2f]\n" , defaults->rc.f_ip_factor ); H2( " --pbratio QP factor between P and B [%.2f]\n" , defaults->rc.f_pb_factor ); H2( " --chroma-qp-offset QP difference between chroma and luma [%d]\n" , defaults->analyse.i_chroma_qp_offset ); H2( " --aq-mode AQ method [%d]\n" " - 0: Disabled\n" " - 1: Variance AQ (complexity mask)\n" " - 2: Auto-variance AQ (experimental)\n", defaults->rc.i_aq_mode ); H1( " --aq-strength Reduces blocking and blurring in flat and\n" " textured areas. [%.1f]\n", defaults->rc.f_aq_strength ); H1( "\n" ); H0( " -p, --pass Enable multipass ratecontrol\n" " - 1: First pass, creates stats file\n" " - 2: Last pass, does not overwrite stats file\n" ); H2( " - 3: Nth pass, overwrites stats file\n" ); H1( " --stats Filename for 2 pass stats [\"%s\"]\n" , defaults->rc.psz_stat_out ); H2( " --no-mbtree Disable mb-tree ratecontrol.\n"); H2( " --qcomp QP curve compression [%.2f]\n" , defaults->rc.f_qcompress ); H2( " --cplxblur Reduce fluctuations in QP (before curve compression) [%.1f]\n" , defaults->rc.f_complexity_blur ); H2( " --qblur Reduce fluctuations in QP (after curve compression) [%.1f]\n" , defaults->rc.f_qblur ); H2( " --zones //... Tweak the bitrate of regions of the video\n" ); H2( " Each zone is of the form\n" " ,, " where " q= (force QP)\n" " or b= (bitrate multiplier)\n" ); H2( " --qpfile Force frametypes and QPs for some or all frames\n" " Format of each line: framenumber frametype QP\n" " QP is optional (none lets x264 choose). Frametypes: I,i,K,P,B,b.\n" " K= depending on open-gop setting\n" " QPs are restricted by qpmin/qpmax.\n" ); H1( "\n" ); H1( "Analysis:\n" ); H1( "\n" ); H1( " -A, --partitions Partitions to consider [\"p8x8,b8x8,i8x8,i4x4\"]\n" " - p8x8, p4x4, b8x8, i8x8, i4x4\n" " - none, all\n" " (p4x4 requires p8x8. i8x8 requires --8x8dct.)\n" ); H1( " --direct Direct MV prediction mode [\"%s\"]\n" " - none, spatial, temporal, auto\n", strtable_lookup( x264_direct_pred_names, defaults->analyse.i_direct_mv_pred ) ); H2( " --no-weightb Disable weighted prediction for B-frames\n" ); H1( " --weightp Weighted prediction for P-frames [%d]\n" " - 0: Disabled\n" " 再分享一下我老师大神的人工智能教程吧。零基础！通俗易懂！风趣幽默！还带黄段子！希望你也加入到我们人工智能的队伍中来！https://blog.csdn.net/jiangjunshow