学习ffmpeg官方示例transcoding.c遇到的问题和解决方法

最近学习ffmpeg，官网提供的示例代码transcoding.c演示了编解码和滤波器的使用，不过第一步的编译运行测试就卡了好久，今天终于找到了原因了，赶紧记录一下，我相信和我遇到同样问题的人不在少数，所以希望能为大家提供一篇有效的解决方案，减轻入门时的痛苦。

把官网示例拷一份在本地，以相同的名字命名为transcoding.c, 因为官网的这个示例，用的是ffmpeg2.x的API，因为我也不太熟悉ffmpeg，用ffmpeg3.x编译时，提示了我几个API过时的问题，所以我装回了ffmpeg2.8.6来编译这个示例。下面是我的编译命令：

gcc -I /usr/local/include/ -L /usr/local/lib -lavformat -lavfilter -lavutil -lswscale -lavcodec transcoding.c -o transcoding    

生成了名为transcoding的二进制可执行文件，我使用自己的一个测试视频运行它：

./transcoding test.mp4 output.mp4

运行结果如下：

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isomavc1
    creation_time   : 2016-01-10 07:17:18
    encoder         : FormatFactory : www.pcfreetime.com
  Duration: 00:01:41.49, start: 0.000000, bitrate: 863 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 856x480 [SAR 480:481 DAR 856:481], 744 kb/s, SAR 427:428 DAR 427:240, 24 fps, 24 tbr, 24k tbn, 48 tbc (default)
    Metadata:
      creation_time   : 2016-01-10 07:17:18
      handler_name    : video
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 116 kb/s (default)
    Metadata:
      creation_time   : 2016-01-10 07:17:18
      handler_name    : sound
[libx264 @ 0x7fe4ac851600] broken ffmpeg default settings detected
[libx264 @ 0x7fe4ac851600] use an encoding preset (e.g. -vpre medium)
[libx264 @ 0x7fe4ac851600] preset usage: -vpre  -vpre 
[libx264 @ 0x7fe4ac851600] speed presets are listed in x264 --help
[libx264 @ 0x7fe4ac851600] profile is optional; x264 defaults to high
Cannot open video encoder for stream #0
Error occurred: Generic error in an external library

#issue 1 - [libx264 @ 0x7fe4ac851600] broken ffmpeg default settings detected

这个错误及其下面的信息告诉我们，在打开输出文件的视频编码器时出现了错误，这通常是由于编码器参数设置不当造成的。通过搜索，发现了这篇文章对这个问题解释的比较清楚:
http://blog.csdn.net/cffishappy/article/details/7680097

解决方法:

在transcoding.c中的open_output_file函数中，修改的部分如下(只增加了13-17行)：

if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
                enc_ctx->height = dec_ctx->height;
                enc_ctx->width = dec_ctx->width;
                enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;
                /* take first format from list of supported formats */
                if (encoder->pix_fmts)
                    enc_ctx->pix_fmt = encoder->pix_fmts[0];
                else
                    enc_ctx->pix_fmt = dec_ctx->pix_fmt;
                /* video time_base can be set to whatever is handy and supported by encoder */
                enc_ctx->time_base = dec_ctx->time_base;

                enc_ctx->me_range = 16; 
                enc_ctx->max_qdiff = 4;
                enc_ctx->qmin = 10; 
                enc_ctx->qmax = 51; 
                enc_ctx->qcompress = 0.6;

            } else {
                enc_ctx->sample_rate = dec_ctx->sample_rate;
                enc_ctx->channel_layout = dec_ctx->channel_layout;
                enc_ctx->channels = av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
                /* take first format from list of supported formats */
                enc_ctx->sample_fmt = encoder->sample_fmts[0];
                enc_ctx->time_base = (AVRational){1, enc_ctx->sample_rate};
            }   

之后，我们保存编译再次运行结果如下：

...
Encoding frame
Pulling filtered frame from filters
Pushing decoded frame to filters
Pulling filtered frame from filters
Encoding frame
[mp4 @ 0x7fbe86803e00] Malformed AAC bitstream detected: use the audio bitstream filter 'aac_adtstoasc' to fix it ('-bsf:a aac_adtstoasc' option with ffmpeg)
[libx264 @ 0x7fbe86804400] frame I:1     Avg QP:45.67  size:  5439
[libx264 @ 0x7fbe86804400] frame P:1     Avg QP:46.05  size:   174
[libx264 @ 0x7fbe86804400] mb I  I16..4: 71.7% 26.7%  1.5%
[libx264 @ 0x7fbe86804400] mb P  I16..4:  0.2%  0.0%  0.0%  P16..4:  5.2%  0.2%  0.0%  0.0%  0.0%    skip:94.4%
[libx264 @ 0x7fbe86804400] final ratefactor: 56.92
[libx264 @ 0x7fbe86804400] 8x8 transform intra:26.7%
[libx264 @ 0x7fbe86804400] coded y,uvDC,uvAC intra: 8.4% 33.3% 10.1% inter: 0.0% 0.1% 0.0%
[libx264 @ 0x7fbe86804400] i16 v,h,dc,p: 39% 34%  7% 19%
[libx264 @ 0x7fbe86804400] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  6% 15% 22% 10% 10%  7% 16%  5%  9%
[libx264 @ 0x7fbe86804400] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu:  8% 33% 12% 10%  8%  8% 15%  2%  4%
[libx264 @ 0x7fbe86804400] i8c dc,h,v,p: 70% 16% 11%  3%
[libx264 @ 0x7fbe86804400] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x7fbe86804400] kb/s:538.85
[libfaac @ 0x7fbe862d2600] 4 frames left in the queue on closing
Error occurred: Operation not permitted

这次的视频编码可以打开并正常编码了，可是音频部分又出现了问题，关于这个问题的解答可以看这个文章：
http://www.tuicool.com/articles/NNNVv2z

博主跟踪发现了困扰我许久的问题，在这里顺便感谢一下。

#issue2 - [mp4 @ 0x7fbe86803e00] Malformed AAC bitstream detected

这个问题在网上搜了好久，stackoverflow中提供了一种方法，可以使程序正常运行，但处理结果中只有音频被保留, 这显然不是我想要的。

其实，只需要调整一下代码顺序就可以了。知道真相的我眼泪掉下来。

解决方法

还是在transcoding.c中的open_output_file函数中，只是把for循环尾部的那句代码：

if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
                enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; 

提前到for循环中整个if判断结构的前面就行了，因为我们在打开编码器前，没有设置编码器上下文中enc_ctx->flags这个参数，所以把这句提前了就解决问题了。如下：

            if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
                enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;

            if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
                enc_ctx->height = dec_ctx->height;
                enc_ctx->width = dec_ctx->width;
                enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;
                /* take first format from list of supported formats */
                if (encoder->pix_fmts)
                    enc_ctx->pix_fmt = encoder->pix_fmts[0];
                else
                    enc_ctx->pix_fmt = dec_ctx->pix_fmt;
                /* video time_base can be set to whatever is handy and supported by encoder */
                enc_ctx->time_base = dec_ctx->time_base;

                enc_ctx->me_range = 16;
                enc_ctx->max_qdiff = 4;
                enc_ctx->qmin = 10;
                enc_ctx->qmax = 51;
                enc_ctx->qcompress = 0.6;

            } else {
                enc_ctx->sample_rate = dec_ctx->sample_rate;
                enc_ctx->channel_layout = dec_ctx->channel_layout;
                enc_ctx->channels = av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
                /* take first format from list of supported formats */
                enc_ctx->sample_fmt = encoder->sample_fmts[0];
                enc_ctx->time_base = (AVRational){1, enc_ctx->sample_rate};
            }

#issue3 - 处理后的结果比原视频模糊

在经过以上两个问题的解决后，编译通过是没有问题了，不过你可能会不满意输出视频的质量，觉得它比原视频模糊了许多，这时我们可以调节\#issue1中的代码：

 enc_ctx->qmax = 51; 

把这个参数改小点，可以减小编码时的量化间隔，提高编码视频的质量，不过你可能因此加长整个编码的时间。

例如我将其改为：

 enc_ctx->qmax = 30;

最后附上修改后的完整代码：

filename: transcoding.c

/*
 * Copyright (c) 2010 Nicolas George
 * Copyright (c) 2011 Stefano Sabatini
 * Copyright (c) 2014 Andrey Utkin
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
/**
 * @file
 * API example for demuxing, decoding, filtering, encoding and muxing
 * @example transcoding.c
 */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
static AVFormatContext *ifmt_ctx;
static AVFormatContext *ofmt_ctx;
typedef struct FilteringContext {
    AVFilterContext *buffersink_ctx;
    AVFilterContext *buffersrc_ctx;
    AVFilterGraph *filter_graph;
} FilteringContext;
static FilteringContext *filter_ctx;
static int open_input_file(const char *filename)
{
    int ret;
    unsigned int i;
    ifmt_ctx = NULL;
    if ((ret = avformat_open_input(&ifmt_ctx, filename, NULL, NULL)) < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
        return ret;
    }
    if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
        return ret;
    }
    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        AVStream *stream;
        AVCodecContext *codec_ctx;
        stream = ifmt_ctx->streams[i];
        codec_ctx = stream->codec;
        /* Reencode video & audio and remux subtitles etc. */
        if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
                || codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
            /* Open decoder */
            ret = avcodec_open2(codec_ctx,
                    avcodec_find_decoder(codec_ctx->codec_id), NULL);
            if (ret < 0) {
                av_log(NULL, AV_LOG_ERROR, "Failed to open decoder for stream #%u\n", i);
                return ret;
            }
        }
    }
    av_dump_format(ifmt_ctx, 0, filename, 0);
    return 0;
}
static int open_output_file(const char *filename)
{
    AVStream *out_stream;
    AVStream *in_stream;
    AVCodecContext *dec_ctx, *enc_ctx;
    AVCodec *encoder;
    int ret;
    unsigned int i;
    ofmt_ctx = NULL;
    avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, filename);
    if (!ofmt_ctx) {
        av_log(NULL, AV_LOG_ERROR, "Could not create output context\n");
        return AVERROR_UNKNOWN;
    }
    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        out_stream = avformat_new_stream(ofmt_ctx, NULL);
        if (!out_stream) {
            av_log(NULL, AV_LOG_ERROR, "Failed allocating output stream\n");
            return AVERROR_UNKNOWN;
        }
        in_stream = ifmt_ctx->streams[i];
        dec_ctx = in_stream->codec;
        enc_ctx = out_stream->codec;
        if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
                || dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
            /* in this example, we choose transcoding to same codec */
            encoder = avcodec_find_encoder(dec_ctx->codec_id);
            if (!encoder) {
                av_log(NULL, AV_LOG_FATAL, "Necessary encoder not found\n");
                return AVERROR_INVALIDDATA;
            }
            /* In this example, we transcode to same properties (picture size,
             * sample rate etc.). These properties can be changed for output
             * streams easily using filters */

        if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
            enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;

            if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
                enc_ctx->height = dec_ctx->height;
                enc_ctx->width = dec_ctx->width;
                enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;
                /* take first format from list of supported formats */
                if (encoder->pix_fmts)
                    enc_ctx->pix_fmt = encoder->pix_fmts[0];
                else
                    enc_ctx->pix_fmt = dec_ctx->pix_fmt;
                /* video time_base can be set to whatever is handy and supported by encoder */
                enc_ctx->time_base = dec_ctx->time_base;

                enc_ctx->me_range = 16;
                enc_ctx->max_qdiff = 4;
                enc_ctx->qmin = 10;
                enc_ctx->qmax = 51;
                enc_ctx->qcompress = 0.6;

            } else {
                enc_ctx->sample_rate = dec_ctx->sample_rate;
                enc_ctx->channel_layout = dec_ctx->channel_layout;
                enc_ctx->channels = av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
                /* take first format from list of supported formats */
                enc_ctx->sample_fmt = encoder->sample_fmts[0];
                enc_ctx->time_base = (AVRational){1, enc_ctx->sample_rate};
            }
            /* Third parameter can be used to pass settings to encoder */
            ret = avcodec_open2(enc_ctx, encoder, NULL);
            if (ret < 0) {
                av_log(NULL, AV_LOG_ERROR, "Cannot open video encoder for stream #%u\n", i);
                return ret;
            }
        } else if (dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN) {
            av_log(NULL, AV_LOG_FATAL, "Elementary stream #%d is of unknown type, cannot proceed\n", i);
            return AVERROR_INVALIDDATA;
        } else {
            /* if this stream must be remuxed */
            ret = avcodec_copy_context(ofmt_ctx->streams[i]->codec,
                    ifmt_ctx->streams[i]->codec);
            if (ret < 0) {
                av_log(NULL, AV_LOG_ERROR, "Copying stream context failed\n");
                return ret;
            }
        }
    }
    av_dump_format(ofmt_ctx, 0, filename, 1);
    if (!(ofmt_ctx->oformat->flags & AVFMT_NOFILE)) {
        ret = avio_open(&ofmt_ctx->pb, filename, AVIO_FLAG_WRITE);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Could not open output file '%s'", filename);
            return ret;
        }
    }
    /* init muxer, write output file header */
    ret = avformat_write_header(ofmt_ctx, NULL);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Error occurred when opening output file\n");
        return ret;
    }
    return 0;
}
static int init_filter(FilteringContext* fctx, AVCodecContext *dec_ctx,
        AVCodecContext *enc_ctx, const char *filter_spec)
{
    char args[512];
    int ret = 0;
    AVFilter *buffersrc = NULL;
    AVFilter *buffersink = NULL;
    AVFilterContext *buffersrc_ctx = NULL;
    AVFilterContext *buffersink_ctx = NULL;
    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs  = avfilter_inout_alloc();
    AVFilterGraph *filter_graph = avfilter_graph_alloc();
    if (!outputs || !inputs || !filter_graph) {
        ret = AVERROR(ENOMEM);
        goto end;
    }
    if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
        buffersrc = avfilter_get_by_name("buffer");
        buffersink = avfilter_get_by_name("buffersink");
        if (!buffersrc || !buffersink) {
            av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
            ret = AVERROR_UNKNOWN;
            goto end;
        }
        snprintf(args, sizeof(args),
                "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
                dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
                dec_ctx->time_base.num, dec_ctx->time_base.den,
                dec_ctx->sample_aspect_ratio.num,
                dec_ctx->sample_aspect_ratio.den);
        ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
                args, NULL, filter_graph);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
            goto end;
        }
        ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
                NULL, NULL, filter_graph);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
            goto end;
        }
        ret = av_opt_set_bin(buffersink_ctx, "pix_fmts",
                (uint8_t*)&enc_ctx->pix_fmt, sizeof(enc_ctx->pix_fmt),
                AV_OPT_SEARCH_CHILDREN);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
            goto end;
        }
    } else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
        buffersrc = avfilter_get_by_name("abuffer");
        buffersink = avfilter_get_by_name("abuffersink");
        if (!buffersrc || !buffersink) {
            av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
            ret = AVERROR_UNKNOWN;
            goto end;
        }
        if (!dec_ctx->channel_layout)
            dec_ctx->channel_layout =
                av_get_default_channel_layout(dec_ctx->channels);
        snprintf(args, sizeof(args),
                "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
                dec_ctx->time_base.num, dec_ctx->time_base.den, dec_ctx->sample_rate,
                av_get_sample_fmt_name(dec_ctx->sample_fmt),
                dec_ctx->channel_layout);
        ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
                args, NULL, filter_graph);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
            goto end;
        }
        ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
                NULL, NULL, filter_graph);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
            goto end;
        }
        ret = av_opt_set_bin(buffersink_ctx, "sample_fmts",
                (uint8_t*)&enc_ctx->sample_fmt, sizeof(enc_ctx->sample_fmt),
                AV_OPT_SEARCH_CHILDREN);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
            goto end;
        }
        ret = av_opt_set_bin(buffersink_ctx, "channel_layouts",
                (uint8_t*)&enc_ctx->channel_layout,
                sizeof(enc_ctx->channel_layout), AV_OPT_SEARCH_CHILDREN);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
            goto end;
        }
        ret = av_opt_set_bin(buffersink_ctx, "sample_rates",
                (uint8_t*)&enc_ctx->sample_rate, sizeof(enc_ctx->sample_rate),
                AV_OPT_SEARCH_CHILDREN);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
            goto end;
        }
    } else {
        ret = AVERROR_UNKNOWN;
        goto end;
    }
    /* Endpoints for the filter graph. */
    outputs->name       = av_strdup("in");
    outputs->filter_ctx = buffersrc_ctx;
    outputs->pad_idx    = 0;
    outputs->next       = NULL;
    inputs->name       = av_strdup("out");
    inputs->filter_ctx = buffersink_ctx;
    inputs->pad_idx    = 0;
    inputs->next       = NULL;
    if (!outputs->name || !inputs->name) {
        ret = AVERROR(ENOMEM);
        goto end;
    }
    if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_spec,
                    &inputs, &outputs, NULL)) < 0)
        goto end;
    if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
        goto end;
    /* Fill FilteringContext */
    fctx->buffersrc_ctx = buffersrc_ctx;
    fctx->buffersink_ctx = buffersink_ctx;
    fctx->filter_graph = filter_graph;
end:
    avfilter_inout_free(&inputs);
    avfilter_inout_free(&outputs);
    return ret;
}
static int init_filters(void)
{
    const char *filter_spec;
    unsigned int i;
    int ret;
    filter_ctx = av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_ctx));
    if (!filter_ctx)
        return AVERROR(ENOMEM);
    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        filter_ctx[i].buffersrc_ctx  = NULL;
        filter_ctx[i].buffersink_ctx = NULL;
        filter_ctx[i].filter_graph   = NULL;
        if (!(ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO
                || ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO))
            continue;
        if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
            filter_spec = "null"; /* passthrough (dummy) filter for video */
        else
            filter_spec = "anull"; /* passthrough (dummy) filter for audio */
        ret = init_filter(&filter_ctx[i], ifmt_ctx->streams[i]->codec,
                ofmt_ctx->streams[i]->codec, filter_spec);
        if (ret)
            return ret;
    }
    return 0;
}
static int encode_write_frame(AVFrame *filt_frame, unsigned int stream_index, int *got_frame) {
    int ret;
    int got_frame_local;
    AVPacket enc_pkt;
    int (*enc_func)(AVCodecContext *, AVPacket *, const AVFrame *, int *) =
        (ifmt_ctx->streams[stream_index]->codec->codec_type ==
         AVMEDIA_TYPE_VIDEO) ? avcodec_encode_video2 : avcodec_encode_audio2;
    if (!got_frame)
        got_frame = &got_frame_local;
    av_log(NULL, AV_LOG_INFO, "Encoding frame\n");
    /* encode filtered frame */
    enc_pkt.data = NULL;
    enc_pkt.size = 0;
    av_init_packet(&enc_pkt);
    ret = enc_func(ofmt_ctx->streams[stream_index]->codec, &enc_pkt,
            filt_frame, got_frame);
    av_frame_free(&filt_frame);
    if (ret < 0)
        return ret;
    if (!(*got_frame))
        return 0;
    /* prepare packet for muxing */
    enc_pkt.stream_index = stream_index;
    av_packet_rescale_ts(&enc_pkt,
                         ofmt_ctx->streams[stream_index]->codec->time_base,
                         ofmt_ctx->streams[stream_index]->time_base);
    av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n");
    /* mux encoded frame */
    ret = av_interleaved_write_frame(ofmt_ctx, &enc_pkt);
    return ret;
}
static int filter_encode_write_frame(AVFrame *frame, unsigned int stream_index)
{
    int ret;
    AVFrame *filt_frame;
    av_log(NULL, AV_LOG_INFO, "Pushing decoded frame to filters\n");
    /* push the decoded frame into the filtergraph */
    ret = av_buffersrc_add_frame_flags(filter_ctx[stream_index].buffersrc_ctx,
            frame, 0);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
        return ret;
    }
    /* pull filtered frames from the filtergraph */
    while (1) {
        filt_frame = av_frame_alloc();
        if (!filt_frame) {
            ret = AVERROR(ENOMEM);
            break;
        }
        av_log(NULL, AV_LOG_INFO, "Pulling filtered frame from filters\n");
        ret = av_buffersink_get_frame(filter_ctx[stream_index].buffersink_ctx,
                filt_frame);
        if (ret < 0) {
            /* if no more frames for output - returns AVERROR(EAGAIN)
             * if flushed and no more frames for output - returns AVERROR_EOF
             * rewrite retcode to 0 to show it as normal procedure completion
             */
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                ret = 0;
            av_frame_free(&filt_frame);
            break;
        }
        filt_frame->pict_type = AV_PICTURE_TYPE_NONE;
        ret = encode_write_frame(filt_frame, stream_index, NULL);
        if (ret < 0)
            break;
    }
    return ret;
}
static int flush_encoder(unsigned int stream_index)
{
    int ret;
    int got_frame;
    if (!(ofmt_ctx->streams[stream_index]->codec->codec->capabilities &
                AV_CODEC_CAP_DELAY))
        return 0;
    while (1) {
        av_log(NULL, AV_LOG_INFO, "Flushing stream #%u encoder\n", stream_index);
        ret = encode_write_frame(NULL, stream_index, &got_frame);
        if (ret < 0)
            break;
        if (!got_frame)
            return 0;
    }
    return ret;
}
int main(int argc, char **argv)
{
    int ret;
    AVPacket packet = { .data = NULL, .size = 0 };
    AVFrame *frame = NULL;
    enum AVMediaType type;
    unsigned int stream_index;
    unsigned int i;
    int got_frame;
    int (*dec_func)(AVCodecContext *, AVFrame *, int *, const AVPacket *);
    if (argc != 3) {
        av_log(NULL, AV_LOG_ERROR, "Usage: %s  
\n", argv[0]);
        return 1;
    }
    av_register_all();
    avfilter_register_all();
    if ((ret = open_input_file(argv[1])) < 0)
        goto end;
    if ((ret = open_output_file(argv[2])) < 0)
        goto end;
    if ((ret = init_filters()) < 0)
        goto end;
    /* read all packets */
    while (1) {
        if ((ret = av_read_frame(ifmt_ctx, &packet)) < 0)
            break;
        stream_index = packet.stream_index;
        type = ifmt_ctx->streams[packet.stream_index]->codec->codec_type;
        av_log(NULL, AV_LOG_DEBUG, "Demuxer gave frame of stream_index %u\n",
                stream_index);
        if (filter_ctx[stream_index].filter_graph) {
            av_log(NULL, AV_LOG_DEBUG, "Going to reencode&filter the frame\n");
            frame = av_frame_alloc();
            if (!frame) {
                ret = AVERROR(ENOMEM);
                break;
            }
            av_packet_rescale_ts(&packet,
                                 ifmt_ctx->streams[stream_index]->time_base,
                                 ifmt_ctx->streams[stream_index]->codec->time_base);
            dec_func = (type == AVMEDIA_TYPE_VIDEO) ? avcodec_decode_video2 :
                avcodec_decode_audio4;
            ret = dec_func(ifmt_ctx->streams[stream_index]->codec, frame,
                    &got_frame, &packet);
            if (ret < 0) {
                av_frame_free(&frame);
                av_log(NULL, AV_LOG_ERROR, "Decoding failed\n");
                break;
            }
            if (got_frame) {
                frame->pts = av_frame_get_best_effort_timestamp(frame);
                ret = filter_encode_write_frame(frame, stream_index);
                av_frame_free(&frame);
                if (ret < 0)
                    goto end;
            } else {
                av_frame_free(&frame);
            }
        } else {
            /* remux this frame without reencoding */
            av_packet_rescale_ts(&packet,
                                 ifmt_ctx->streams[stream_index]->time_base,
                                 ofmt_ctx->streams[stream_index]->time_base);
            ret = av_interleaved_write_frame(ofmt_ctx, &packet);
            if (ret < 0)
                goto end;
        }
        av_packet_unref(&packet);
    }
    /* flush filters and encoders */
    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        /* flush filter */
        if (!filter_ctx[i].filter_graph)
            continue;
        ret = filter_encode_write_frame(NULL, i);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Flushing filter failed\n");
            goto end;
        }
        /* flush encoder */
        ret = flush_encoder(i);
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "Flushing encoder failed\n");
            goto end;
        }
    }
    av_write_trailer(ofmt_ctx);
end:
    av_packet_unref(&packet);
    av_frame_free(&frame);
    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        avcodec_close(ifmt_ctx->streams[i]->codec);
        if (ofmt_ctx && ofmt_ctx->nb_streams > i && ofmt_ctx->streams[i] && ofmt_ctx->streams[i]->codec)
            avcodec_close(ofmt_ctx->streams[i]->codec);
        if (filter_ctx && filter_ctx[i].filter_graph)
            avfilter_graph_free(&filter_ctx[i].filter_graph);
    }
    av_free(filter_ctx);
    avformat_close_input(&ifmt_ctx);
    if (ofmt_ctx && !(ofmt_ctx->oformat->flags & AVFMT_NOFILE))
        avio_closep(&ofmt_ctx->pb);
    avformat_free_context(ofmt_ctx);
    if (ret < 0)
        av_log(NULL, AV_LOG_ERROR, "Error occurred: %s\n", av_err2str(ret));
    return ret ? 1 : 0;
}