libavcodec 提供了一系列编码器的实现
libavformat 实现流协议，容器格式及其本IO访问
libavutil 包含了hash器，解码器和各种工具函数
libavfilter 提供各种音视频过虑器
libavdevice 提供了访问捕获设备和回放设备的接口
libswresample 实现了混音和重采样
libswscale 实现了色彩转换和缩放功能
1.FFmpeg 开发入门Log系统
av_log_set_level(AV_LOG_DEBUG)
av_log(NULL,AV_LOG_INFO,"%s/n",option)
阀值 以上的日志都会打印出来（比如比debug高的error等信息）；
程序内容：
#include
#include
int main(int argc,char *argv[]){
av_log_set_level(AV_LOG_DEBUG);
av_log(NULL,AV_LOG_INFO,"hello world\n");
return 0;
}
使用命令编译：clang -g -o ffmpeg_log f -lavutil
运行程序：./ffmpeg_log
2.FFmpeg 文件的删除与重命名
avpriv_io_delete()
avpriv_io_move()
程序内容：
#include
int main(int argc, char *argv[]){
int ret = avpriv_io_delete("./myfile.txt");
if(ret < 0){
av_log(NULL,AV_LOG_ERROR,"fail to delete file");
//如果ret小于0，则是出错的情况
return -1;
}
return 0;
}
使用命令编译：clang -g -o ffmpeg_file ffmpeg_file.c pkg-config --libs libavformat
运行程序：./ffmpeg_file
提示：brew安装 brew install pkg-config
3.FFmpeg操作目录以及list 的实现
avio_open_dir()
avio_read_dir()
avio_close_dir()
AVIODirContext //操作目录的上下文
AVIODirEntry //目录项、用于存放文件名、文件大小信息
程序内容：
#include
#include
int main (int argc ,char *argv[]){
int ret;
AVIODirContext *ctx = NULL;
AVIODirEntry *entry = NULL;
av_log_set_level(AV_LOG_INFO);
ret = avio_open_dir(&ctx,"./",NULL);
if(ret<0){
av_log(NULL,AV_LOG_ERROR,"cant open dir%s\n",av_err2str(ret));
return -1;
}
while(1){
ret = avio_read_dir(ctx,&entry);
if(ret<0){
av_log(NULL,AV_LOG_ERROR,"cant read dir :%s",av_err2str(ret));
goto __fail;
}
if(!entry){
break;
}
av_log(NULL,AV_LOG_INFO,"%12"PRId64" %s \n",entry->size,entry->name);
avio_free_directory_entry(&entry);
}
__fail:
avio_close_dir(&ctx);
return 0 ;
}
使用命令编译： clang -g -o ffmpeg_list ffmpeg_list.c pkg-config --libs libavformat libavutil
运行程序：./ffmpeg_list
4.FFmpeg处理流数据
AVFormatContext //格式上下文
AVStream //流
AVPacket //包
av_register_all() //将FFpmeg中的编解码库协议注册到程序中
avformat_open_input() //获取文件的上下文 AVFormatContext
avformat_close_input() //关闭文件的上下文
av_dump_format() //将多媒体文件的信息打印出来
处理流程：
解复用-> 获取流-> 读数据包 -> 释放资源
程序内容：
#include
#include
int main (int argc,char *argv[]){
int ret;
AVFormatContext *fmt_ctx = NULL;
av_log_set_level(AV_LOG_INFO);
av_register_all();
ret = avformat_open_input(&fmt_ctx,"./input.mp4",NULL,NULL);
if(ret<0){
av_log(NULL,AV_LOG_ERROR,"fail open input input.mp4");
return -1;
}
av_dump_format(fmt_ctx, 0, "./test.mp4",0);
avformat_close_input(&fmt_ctx);
return 0;
}
使用命令编译： clang -g -o mediainfo mediainfo.c pkg-config --libs libavutil libavformat
运行程序：./mediainfo
5.FFmpeg 抽取音频数据
av_init_packet() //初始化一个数据包结构体
av_find_best_stream() //在多媒体文件中找到最好的一路流
av_read_frame()/av_packet_unref() //读取流中的数据包--释放frame的引用计数器
程序内容：(可能会编译不过)
#include
#include
int main (int argc,char *argv[]){
int ret;
char * src = NULL;
char * dst = NULL;
AVFormatContext *fmt_ctx = NULL;
av_log_set_level(AV_LOG_INFO);
av_register_all();
//1.read two params
if(argc<3){
av_log(NULL,AV_LOG_ERROR,"the count of params should be more than three !\n");
}
src = argv[1];
dst = argv[2];
if(!src || !dst){
av_log(NULL,AV_LOG_ERROR,"souce input or destion input is null\n");
return -1;
}
ret = avformat_open_input(&fmt_ctx,src,NULL,NULL);
if(ret<0){
av_log(NULL,AV_LOG_ERROR,"fail open input input.mp4\n");
return -1;
}
FILE *dst_fd = fopen(dst,"wb");
if(!dst_fd){
av_log(NULL,AV_LOG_ERROR,"can't open output file \n");
avformat_close_input(&fmt_ctx);
return -1;
}
//打印输入视频信息
av_dump_format(fmt_ctx, 0, src,0);
//2.get best stream
ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, NULL, 0);
if(ret<0){
av_log(NULL,AV_LOG_ERROR,"find best stream error\n");
avformat_close_input(&fmt_ctx);
fclose(dst_fd);
return -1;
}
//3.write audio data for aac
AVPacket pkt;
int audio_index = ret; //第35行拿到音频流的index
av_init_packet(&pkt);
while(av_read_frame(fmt_ctx,&pkt)>=0){
if(pkt.stream_index == audio_index){
//添加adts头
char adts_header_buf[7];
adts_header(adts_header_buf,pkt.size);
fwrite(adts_header_buf,1,7,dst_fd);
//将音频数据写入文件
int len = fwrite(pkt.data, 1, pkt.size, dst_fd);
if(len != pkt.size){
av_log(NULL,AV_LOG_WARNING,"waring write audio info error\n");
}
}
av_packet_unref(&pkt);
}
avformat_close_input(&fmt_ctx);
if(dst_fd){
//关闭输出文件的写操作；
fclose(dst_fd);
}
return 0;
}
使用命令编译：clang -g -o extra_audio extra_audio.c pkg-config --libs -liavutil avformat
运行程序：./extra_audio input.mp4 output.aac
6.FFmpeg 抽取 H264数据
程序内容：
#include
#include
#include
#include
#ifndef AV_WB32
# define AV_WB32(p, val) do { \
uint32_t d = (val); \
((uint8_t*)(p))[3] = (d); \
((uint8_t*)(p))[2] = (d)>>8; \
((uint8_t*)(p))[1] = (d)>>16; \
((uint8_t*)(p))[0] = (d)>>24; \
} while(0)
#endif
#ifndef AV_RB16
# define AV_RB16(x) \
((((const uint8_t*)(x))[0] << 8) | \
((const uint8_t*)(x))[1])
#endif
static int alloc_and_copy(AVPacket *out,
const uint8_t *sps_pps, uint32_t sps_pps_size,
const uint8_t *in, uint32_t in_size)
{
uint32_t offset = out->size;
uint8_t nal_header_size = offset ? 3 : 4;
int err;
err = av_grow_packet(out, sps_pps_size + in_size + nal_header_size);
if (err < 0)
return err;
if (sps_pps)
memcpy(out->data + offset, sps_pps, sps_pps_size);
memcpy(out->data + sps_pps_size + nal_header_size + offset, in, in_size);
if (!offset) {
AV_WB32(out->data + sps_pps_size, 1);
} else {
(out->data + offset + sps_pps_size)[0] =
(out->data + offset + sps_pps_size)[1] = 0;
(out->data + offset + sps_pps_size)[2] = 1;
}
return 0;
}
int h264_extradata_to_annexb(const uint8_t *codec_extradata, const int codec_extradata_size, AVPacket *out_extradata, int padding)
{
uint16_t unit_size;
uint64_t total_size = 0;
uint8_t *out = NULL, unit_nb, sps_done = 0,
sps_seen = 0, pps_seen = 0, sps_offset = 0, pps_offset = 0;
const uint8_t *extradata = codec_extradata + 4;
static const uint8_t nalu_header[4] = { 0, 0, 0, 1 };
int length_size = (*extradata++ & 0x3) + 1; // retrieve length coded size, 用于指示表示编码数据长度所需字节数
sps_offset = pps_offset = -1;
/* retrieve sps and pps unit(s) */
unit_nb = *extradata++ & 0x1f; /* number of sps unit(s) */
if (!unit_nb) {
goto pps;
}else {
sps_offset = 0;
sps_seen = 1;
}
while (unit_nb--) {
int err;
unit_size = AV_RB16(extradata);
total_size += unit_size + 4;
if (total_size > INT_MAX - padding) {
av_log(NULL, AV_LOG_ERROR,
"Too big extradata size, corrupted stream or invalid MP4/AVCC bitstream\n");
av_free(out);
return AVERROR(EINVAL);
}
if (extradata + 2 + unit_size > codec_extradata + codec_extradata_size) {
av_log(NULL, AV_LOG_ERROR, "Packet header is not contained in global extradata, "
"corrupted stream or invalid MP4/AVCC bitstream\n");
av_free(out);
return AVERROR(EINVAL);
}
if ((err = av_reallocp(&out, total_size + padding)) < 0)
return err;
memcpy(out + total_size - unit_size - 4, nalu_header, 4);
memcpy(out + total_size - unit_size, extradata + 2, unit_size);
extradata += 2 + unit_size;
pps:
if (!unit_nb && !sps_done++) {
unit_nb = *extradata++; /* number of pps unit(s) */
if (unit_nb) {
pps_offset = total_size;
pps_seen = 1;
}
}
}
if (out)
memset(out + total_size, 0, padding);
if (!sps_seen)
av_log(NULL, AV_LOG_WARNING,
"Warning: SPS NALU missing or invalid. "
"The resulting stream may not play.\n");
if (!pps_seen)
av_log(NULL, AV_LOG_WARNING,
"Warning: PPS NALU missing or invalid. "
"The resulting stream may not play.\n");
out_extradata->data = out;
out_extradata->size = total_size;
return length_size;
}
int h264_mp4toannexb(AVFormatContext *fmt_ctx, AVPacket *in, FILE *dst_fd)
{
AVPacket *out = NULL;
AVPacket spspps_pkt;
int len;
uint8_t unit_type;
int32_t nal_size;
uint32_t cumul_size = 0;
const uint8_t *buf;
const uint8_t *buf_end;
int buf_size;
int ret = 0, i;
out = av_packet_alloc();
buf = in->data;
buf_size = in->size;
buf_end = in->data + in->size;
do {
ret= AVERROR(EINVAL);
if (buf + 4 > buf_end)
goto fail;
for (nal_size = 0, i = 0; i<4; i++)
nal_size = (nal_size << 8) | buf[i];
buf += 4;
unit_type = *buf & 0x1f;
if (nal_size > buf_end - buf || nal_size < 0)
goto fail;
if (unit_type == 5) {
h264_extradata_to_annexb( fmt_ctx->streams[in->stream_index]->codec->extradata,
fmt_ctx->streams[in->stream_index]->codec->extradata_size,
&spspps_pkt,
AV_INPUT_BUFFER_PADDING_SIZE);
if ((ret=alloc_and_copy(out,
spspps_pkt.data, spspps_pkt.size,
buf, nal_size)) < 0)
{
goto fail;
}
/* if only SPS has been seen, also insert PPS */
}
else {
if ((ret=alloc_and_copy(out, NULL, 0, buf, nal_size)) < 0)
goto fail;
}
len = fwrite( out->data, 1, out->size, dst_fd);
if(len != out->size){
av_log(NULL, AV_LOG_DEBUG, "warning, length of writed data isn't equal pkt.size(%d, %d)\n",
len,
out->size);
}
fflush(dst_fd);
next_nal:
buf += nal_size;
cumul_size += nal_size + 4;//s->length_size;
} while (cumul_size < buf_size);
fail:
av_packet_free(&out);
return ret;
}
int main(int argc, char *argv[])
{
int err_code;
char errors[1024];
char *src_filename = NULL;
char *dst_filename = NULL;
FILE *dst_fd = NULL;
int video_stream_index = -1;
AVFormatContext *fmt_ctx = NULL;
AVPacket pkt;
av_log_set_level(AV_LOG_DEBUG);
if(argc < 3){
av_log(NULL, AV_LOG_DEBUG, "the count of parameters should be more than three!\n");
return -1;
}
src_filename = argv[1];
dst_filename = argv[2];
if(src_filename == NULL || dst_filename == NULL){
av_log(NULL, AV_LOG_ERROR, "src or dts file is null, plz check them!\n");
return -1;
}
/*register all formats and codec*/
av_register_all();
dst_fd = fopen(dst_filename, "wb");
if (!dst_fd) {
av_log(NULL, AV_LOG_DEBUG, "Could not open destination file %s\n", dst_filename);
return -1;
}
/*open input media file, and allocate format context*/
if((err_code = avformat_open_input(&fmt_ctx, src_filename, NULL, NULL)) < 0){
av_strerror(err_code, errors, 1024);
av_log(NULL, AV_LOG_DEBUG, "Could not open source file: %s, %d(%s)\n",
src_filename,
err_code,
errors);
return -1;
}
/*dump input information*/
av_dump_format(fmt_ctx, 0, src_filename, 0);
/*initialize packet*/
av_init_packet(&pkt);
pkt.data = NULL;
pkt.size = 0;
/*find best video stream*/
video_stream_index = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
if(video_stream_index < 0){
av_log(NULL, AV_LOG_DEBUG, "Could not find %s stream in input file %s\n",
av_get_media_type_string(AVMEDIA_TYPE_VIDEO),
src_filename);
return AVERROR(EINVAL);
}
/*read frames from media file*/
while(av_read_frame(fmt_ctx, &pkt) >=0 ){
if(pkt.stream_index == video_stream_index){
h264_mp4toannexb(fmt_ctx, &pkt, dst_fd);
}
av_packet_unref(&pkt);
}
/*close input media file*/
avformat_close_input(&fmt_ctx);
if(dst_fd) {
fclose(dst_fd);
}
return 0;
}
使用命令编译：
clang -g -o extr_video extr_video.c pkg-config --libs libavutil libavformat
运行程序：
./extr_video input.mp4 inpu4.h264
ffplay input.h264
7.ffmpeg 将mp4转成flv
avformat_alloc_output_context2() //多媒体输出文件输的的上下文
avformat_free_context() //释放多媒体输出上下文
avformat_new_stream() //输出的多媒体文件中输出新的流
avcodec_parameters_copy() //拷贝多媒体参数
avformat_write_header() //多媒体文件头
av_write_frame()/av_interleaved_write_frame() // 向多媒体文件写入frame数据
av_write_trailer() //写入多媒体文件尾部信息
程序内容：
#include
#include
static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag)
{
AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
tag,
av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
pkt->stream_index);
}
int main(int argc, char **argv)
{
AVOutputFormat *ofmt = NULL;
AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
AVPacket pkt;
const char *in_filename, *out_filename;
int ret, i;
int stream_index = 0;
int *stream_mapping = NULL;
int stream_mapping_size = 0;
if (argc < 3) {
printf("usage: %s input output\n"
"API example program to remux a media file with libavformat and libavcodec.\n"
"The output format is guessed according to the file extension.\n"
"\n", argv[0]);
return 1;
}
in_filename = argv[1];
out_filename = argv[2];
av_register_all();
if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
fprintf(stderr, "Could not open input file '%s'", in_filename);
goto end;
}
if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
fprintf(stderr, "Failed to retrieve input stream information");
goto end;
}
av_dump_format(ifmt_ctx, 0, in_filename, 0);
avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
if (!ofmt_ctx) {
fprintf(stderr, "Could not create output context\n");
ret = AVERROR_UNKNOWN;
goto end;
}
stream_mapping_size = ifmt_ctx->nb_streams;
stream_mapping = av_mallocz_array(stream_mapping_size, sizeof(*stream_mapping));
if (!stream_mapping) {
ret = AVERROR(ENOMEM);
goto end;
}
ofmt = ofmt_ctx->oformat;
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
AVStream *out_stream;
AVStream *in_stream = ifmt_ctx->streams[i];
AVCodecParameters *in_codecpar = in_stream->codecpar;
if (in_codecpar->codec_type != AVMEDIA_TYPE_AUDIO &&
in_codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
in_codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE) {
stream_mapping[i] = -1;
continue;
}
stream_mapping[i] = stream_index++;
out_stream = avformat_new_stream(ofmt_ctx, NULL);
if (!out_stream) {
fprintf(stderr, "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);
if (ret < 0) {
fprintf(stderr, "Failed to copy codec parameters\n");
goto end;
}
out_stream->codecpar->codec_tag = 0;
}
av_dump_format(ofmt_ctx, 0, out_filename, 1);
if (!(ofmt->flags & AVFMT_NOFILE)) {
ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
if (ret < 0) {
fprintf(stderr, "Could not open output file '%s'", out_filename);
goto end;
}
}
ret = avformat_write_header(ofmt_ctx, NULL);
if (ret < 0) {
fprintf(stderr, "Error occurred when opening output file\n");
goto end;
}
while (1) {
AVStream *in_stream, *out_stream;
ret = av_read_frame(ifmt_ctx, &pkt);
if (ret < 0)
break;
in_stream = ifmt_ctx->streams[pkt.stream_index];
if (pkt.stream_index >= stream_mapping_size ||
stream_mapping[pkt.stream_index] < 0) {
av_packet_unref(&pkt);
continue;
}
pkt.stream_index = stream_mapping[pkt.stream_index];
out_stream = ofmt_ctx->streams[pkt.stream_index];
log_packet(ifmt_ctx, &pkt, "in");
/* copy packet */
pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
pkt.pos = -1;
log_packet(ofmt_ctx, &pkt, "out");
ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
if (ret < 0) {
fprintf(stderr, "Error muxing packet\n");
break;
}
av_packet_unref(&pkt);
}
av_write_trailer(ofmt_ctx);
end:
avformat_close_input(&ifmt_ctx);
/* close output */
if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
avio_closep(&ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
av_freep(&stream_mapping);
if (ret < 0 && ret != AVERROR_EOF) {
fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
return 1;
}
return 0;
}
使用命令编译：
clang -g -o remuxing remuxing pkg-config --libs libavutil libavformat
运行程序：
./remuxing input.mp4 output.flv
ffplay output.flv
8.FFmpeg音视频裁剪
程序内容：
#include
#include
#include
static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag)
{
AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
tag,
av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
pkt->stream_index);
}
int cut_video(double from_seconds, double end_seconds, const char* in_filename, const char* out_filename) {
AVOutputFormat *ofmt = NULL;
AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
AVPacket pkt;
int ret, i;
av_register_all();
if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
fprintf(stderr, "Could not open input file '%s'", in_filename);
goto end;
}
if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
fprintf(stderr, "Failed to retrieve input stream information");
goto end;
}
av_dump_format(ifmt_ctx, 0, in_filename, 0);
avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
if (!ofmt_ctx) {
fprintf(stderr, "Could not create output context\n");
ret = AVERROR_UNKNOWN;
goto end;
}
ofmt = ofmt_ctx->oformat;
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
AVStream *in_stream = ifmt_ctx->streams[i];
AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
if (!out_stream) {
fprintf(stderr, "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
ret = avcodec_copy_context(out_stream->codec, in_stream->codec);
if (ret < 0) {
fprintf(stderr, "Failed to copy context from input to output stream codec context\n");
goto end;
}
out_stream->codec->codec_tag = 0;
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
out_stream->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}
av_dump_format(ofmt_ctx, 0, out_filename, 1);
if (!(ofmt->flags & AVFMT_NOFILE)) {
ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
if (ret < 0) {
fprintf(stderr, "Could not open output file '%s'", out_filename);
goto end;
}
}
ret = avformat_write_header(ofmt_ctx, NULL);
if (ret < 0) {
fprintf(stderr, "Error occurred when opening output file\n");
goto end;
}
// int indexs[8] = {0};
// int64_t start_from = 8*AV_TIME_BASE;
ret = av_seek_frame(ifmt_ctx, -1, from_seconds*AV_TIME_BASE, AVSEEK_FLAG_ANY);
if (ret < 0) {
fprintf(stderr, "Error seek\n");
goto end;
}
int64_t *dts_start_from = malloc(sizeof(int64_t) * ifmt_ctx->nb_streams);
memset(dts_start_from, 0, sizeof(int64_t) * ifmt_ctx->nb_streams);
int64_t *pts_start_from = malloc(sizeof(int64_t) * ifmt_ctx->nb_streams);
memset(pts_start_from, 0, sizeof(int64_t) * ifmt_ctx->nb_streams);
while (1) {
AVStream *in_stream, *out_stream;
ret = av_read_frame(ifmt_ctx, &pkt);
if (ret < 0)
break;
in_stream = ifmt_ctx->streams[pkt.stream_index];
out_stream = ofmt_ctx->streams[pkt.stream_index];
log_packet(ifmt_ctx, &pkt, "in");
if (av_q2d(in_stream->time_base) * pkt.pts > end_seconds) {
av_free_packet(&pkt);
break;
}
if (dts_start_from[pkt.stream_index] == 0) {
dts_start_from[pkt.stream_index] = pkt.dts;
printf("dts_start_from: %s\n", av_ts2str(dts_start_from[pkt.stream_index]));
}
if (pts_start_from[pkt.stream_index] == 0) {
pts_start_from[pkt.stream_index] = pkt.pts;
printf("pts_start_from: %s\n", av_ts2str(pts_start_from[pkt.stream_index]));
}
/* copy packet */
pkt.pts = av_rescale_q_rnd(pkt.pts - pts_start_from[pkt.stream_index], in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
pkt.dts = av_rescale_q_rnd(pkt.dts - dts_start_from[pkt.stream_index], in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
if (pkt.pts < 0) {
pkt.pts = 0;
}
if (pkt.dts < 0) {
pkt.dts = 0;
}
pkt.duration = (int)av_rescale_q((int64_t)pkt.duration, in_stream->time_base, out_stream->time_base);
pkt.pos = -1;
log_packet(ofmt_ctx, &pkt, "out");
printf("\n");
ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
if (ret < 0) {
fprintf(stderr, "Error muxing packet\n");
break;
}
av_free_packet(&pkt);
}
free(dts_start_from);
free(pts_start_from);
av_write_trailer(ofmt_ctx);
end:
avformat_close_input(&ifmt_ctx);
/* close output */
if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
avio_closep(&ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
if (ret < 0 && ret != AVERROR_EOF) {
fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
return 1;
}
return 0;
}
int main(int argc, char *argv[]){
if(argc < 5){
fprintf(stderr, "Usage: \
command startime, endtime, srcfile, outfile");
return -1;
}
double startime = atoi(argv[1]);
double endtime = atoi(argv[2]);
cut_video(startime, endtime, argv[3], argv[4]);
return 0;
}
使用命令编译：
运行程序：