include<libavutil/log.h>
av_log_set_level(AV_LOG_DEBUG)
av_log(NULL, AV_LOG_INFO,"...");
AV_LOG_ERROR
AV_LOG_WARNING
AV_LOG_INFO
AV_LOG_DEBUG
具体例子：
ff_log.c :
#include<stdio.h>
#include<libavutil/log.h>
int main(int argc, char *argv[]){
av_log_set_level(AV_LOG_INFO);
av_log(NULL, AV_LOG_DEBUG, "Hello world:%s%d\n","aaa",10);
av_log(NULL, AV_LOG_INFO, "Hello world INFO!\n");
av_log(NULL, AV_LOG_ERROR, "Hello world ERROR!\n");
return 0;
}
vim ff_log.c
clang -g -o ff_log ff_log.c -I/usr/local/ffmpeg/include -L/usr/local/ffmpeg/lib -lavutil
或者：
clang -g -o ff_log ff_log.c `pkg-config --cflags --libs libavutil`
./ff_log
Hello world INFO!
Hello world ERROR!
mac中，使用第二种方式编译链接时报错如下：
Package libavutil was not found in the pkg-config search path.
Perhaps you should add the directory containing `libavutil.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libavutil' found
ff_log.c:2:9: fatal error: 'libavutil/log.h' file not found
#include<libavutil/log.h>
^~~~~~~~~~~~~~~~~
1 error generated.
解决办法如下：
vim ~/.bash_profile
source ~/.bash_profile
在文件中添加最后两行export：
# HomeBrew
export HOMEBREW_BOTTLE_DOMAIN=https://mirrors.ustc.edu.cn/homebrew-bottles
export PATH="/usr/local/bin:$PATH"
export PATH="/usr/local/sbin:$PATH"
export PATH="/usr/local/ffmpeg/bin:$PATH"
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/ffmpeg/lib/pkgconfig
export LD_LIBRARY_PATH=$LIB_LIBRARY_PATH:/usr/local/ffmpeg/lib
# HomeBrew END
文件删除与重命名：
avpriv_io_delete()
avpriv_io_move()
ffmpeg_file.c:
#include<stdio.h>
#include<libavutil/log.h>
#include<libavformat/avformat.h>
int main(int argc, char* argv[]){
int ret;
// 重命名文件
ret = avpriv_io_move("111.txt", "222.txt");
if(ret < 0){
av_log(NULL, AV_LOG_ERROR, "Failed to rename\n");
return -1;
}
av_log(NULL, AV_LOG_INFO, "Success to rename\n");
// 删除文件
// url
ret = avpriv_io_delete("./mytestfile.txt");
if(ret < 0){
av_log(NULL, AV_LOG_ERROR, "Fail to delete file mytestfile.txt\n");
return -1;
}
av_log(NULL, AV_LOG_INFO, "Success to delete mytestfile.txt\n");
return 0;
}
编译运行：
ffmpeg_file % clang -g -o ffmpeg_mov_del ffmpeg_file.c `pkg-config --cflags --libs libavutil --libs libavformat`
./ffmpeg_mov_del
avio_open_dir()
avio_read_dir()
avio_close_dir()
AVIODirContext 操作目录的上下文
AVIODirEntry 目录项 存放文件名，文件大小等信息
ffmpeg_file_list.c:
#include<libavutil/log.h>
#include<libavformat/avformat.h>
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, "Cannot open dir:%s\n", av_err2str(ret));
}
while(1){
ret = avio_read_dir(ctx, &entry);
if(ret < 0){
av_log(NULL, AV_LOG_ERROR, "Cannot read dir:%s\n", 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;
}
编译运行：
clang -g -o ffmpeg_list ffmpeg_file_list.c `pkg-config --cflags --libs libavutil --libs libavformat`
./ffmpeg_list
6148 .DS_Store
96 ffmpeg_del.dSYM
49848 ffmpeg_del
0 222.txt
536 ffmpeg_file.c
689 ffmpeg_file_list.c
50408 ffmpeg_list
96 ffmpeg_list.dSYM
多媒体文件其实就是容器，在容器中有很多流（流Stream/轨Track）；
从流中读出的数据称为包；
在一个包中包含着一个或多个帧。
AVFormatContext 格式上下文
AVStream 流
AVPacket 包
新版本ffmpeg中弃用了这个函数：av_register_all() 所有ffmpeg代码开始前都得先调用此api
avformat_open_input() 和 avformat_close_input() 成对出现
打开多媒体文件，输出结构体AVFormatContext，借助这个格式上下文获取参数信息，最后关闭多媒体文件
av_dump_format() 打印多媒体文件的meta信息
vim mediainfo.c
输入内容如下：
#include<libavutil/log.h>
#include<libavformat/avformat.h>
int main(int argc, char* argv[])
{
int ret;
AVFormatContext *fmt_ctx = NULL; // 定义上下文
av_log_set_level(AV_LOG_INFO); // 设置日志级别
//av_register_all(); // 注册多媒体格式协议，新版本ffmpeg中弃用了这个函数
avformat_open_input(&fmt_ctx,"./test.mp4", NULL, NULL); // 打开多媒体文件 第3个参数NULL:指定输入格式，默认文件后缀名
if(ret<0){ // 如果打开失败，就打印日志信息并退出
av_log(NULL, AV_LOG_ERROR, "Can't open file: %s\n",av_err2str(ret));
return -1;
}
// 打开成功，进入这里，执行下面的逻辑
av_dump_format(fmt_ctx, 0, "./test.mp4", 0); // 打印多诶题文件的meta信息 no2填0记住即可；no4填0表示是输入文件，如果输出文件填1
avformat_close_input(&fmt_ctx); // 关闭多媒体文件
return 0;
}
编译：
clang -g -o mediainfo mediainfo.c `pkg-config --cflags --libs libavutil --libs libavformat`
有个警告：
mediainfo.c:11:2: warning: 'avcodec_register_all' is deprecated
执行：
./mediainfo
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './test.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
comment : vid:v0300fa50000c08eg9qcf5vi1hpn9gfg
encoder : Lavf58.20.100
Duration: 00:00:10.94, bitrate: N/A
Stream #0:0(und): Video: h264 (avc1 / 0x31637661), none, 720x1280, 1174 kb/s, SAR 1:1 DAR 9:16, 29.82 fps, 30 tbr, 15360 tbn (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, 2 channels, 128 kb/s (default)
Metadata:
handler_name : SoundHandler
av_init_packet() 初始化的数据包
av_find_best_stream() 找到想要拿到的最好的一路流
av_read_frame() / av_packet_unref() read获取流中的数据包，做一些处理，本例是写入aac文件；
每次用read读取数据包，会增加引用计数，使用unref可以释放引用计数，让ffmpeg自动释放包，避免内存泄漏
使用课程中的代码抽取音频：
#include<stdio.h>
#include<libavutil/log.h>
#include<libavformat/avformat.h>
#include <libavformat/avio.h>
#define ADTS_HEADER_LEN 7;
void adts_header(char *szAdtsHeader, int dataLen){
int audio_object_type = 2;
int sampling_frequency_index = 7;
int channel_config = 2;
int adtsLen = dataLen + 7;
szAdtsHeader[0] = 0xff; //syncword:0xfff 高8bits
szAdtsHeader[1] = 0xf0; //syncword:0xfff 低4bits
szAdtsHeader[1] |= (0 << 3); //MPEG Version:0 for MPEG-4,1 for MPEG-2 1bit
szAdtsHeader[1] |= (0 << 1); //Layer:0 2bits
szAdtsHeader[1] |= 1; //protection absent:1 1bit
szAdtsHeader[2] = (audio_object_type - 1)<<6; //profile:audio_object_type - 1 2bits
szAdtsHeader[2] |= (sampling_frequency_index & 0x0f)<<2; //sampling frequency index:sampling_frequency_index 4bits
szAdtsHeader[2] |= (0 << 1); //private bit:0 1bit
szAdtsHeader[2] |= (channel_config & 0x04)>>2; //channel configuration:channel_config 高1bit
szAdtsHeader[3] = (channel_config & 0x03)<<6; //channel configuration:channel_config 低2bits
szAdtsHeader[3] |= (0 << 5); //original：0 1bit
szAdtsHeader[3] |= (0 << 4); //home：0 1bit
szAdtsHeader[3] |= (0 << 3); //copyright id bit：0 1bit
szAdtsHeader[3] |= (0 << 2); //copyright id start：0 1bit
szAdtsHeader[3] |= ((adtsLen & 0x1800) >> 11); //frame length：value 高2bits
szAdtsHeader[4] = (uint8_t)((adtsLen & 0x7f8) >> 3); //frame length:value 中间8bits
szAdtsHeader[5] = (uint8_t)((adtsLen & 0x7) << 5); //frame length:value 低3bits
szAdtsHeader[5] |= 0x1f; //buffer fullness:0x7ff 高5bits
szAdtsHeader[6] = 0xfc;
}
int main(int argc, char* argv[])
{
int ret;
int len;
int audio_index;
char* src = NULL;
char* dst = NULL;
AVPacket pkt;
AVFormatContext *fmt_ctx = NULL; // 定义上下文
av_log_set_level(AV_LOG_INFO); // 设置日志级别
// 1:read two params from console
if(argc<3){
av_log(NULL, AV_LOG_ERROR, "the count of params should be 3.\n");
return -1;
}
src = argv[1];
dst = argv[2];
if(!src || !dst){
av_log(NULL, AV_LOG_ERROR, "src or dst is null!\n");
return -1;
}
ret = avformat_open_input(&fmt_ctx, src, NULL, NULL); // 打开多媒文件
if(ret<0){ // 如果打开失败，就打印日志信息并退出
av_log(NULL, AV_LOG_ERROR, "Can't open file: %s\n",av_err2str(ret));
return -1;
}
// 打开成功，进入这里，执行下面的逻辑
FILE* dst_fd = fopen(dst, "wb");
if(!dst_fd){
av_log(NULL, AV_LOG_ERROR, "Can't open out file!\n");
avformat_close_input(&fmt_ctx); // 此时输入流已打开了，需要关闭
return -1;
}
av_dump_format(fmt_ctx, 0, src, 0); // 打印多诶题文件的meta信息 no2填0记住即可；no4填0表示是输入文件，如果输出文件填1
// 2:get stream
ret = av_find_best_stream(fmt_ctx/*上下文*/,
AVMEDIA_TYPE_AUDIO/*想要抽取的流的类型，音频流*/,
-1/*流的索引号，此处不知道*/,
-1/*音频流对应的视频流的索引号，此处不关心*/,
NULL/*流的编解码器，不关心*/,
0/*flag,一些标准，不关心*/ );
if(ret<0){
av_log(NULL, AV_LOG_ERROR, "Cannot find the best stream!\n");
avformat_close_input(&fmt_ctx);
fclose(dst_fd);
return -1;
}
audio_index = ret;
av_init_packet(&pkt);
while(av_read_frame(fmt_ctx, &pkt) >= 0){
if(pkt.stream_index == audio_index){
// 生成adts头，并写入文件
char adts_header_buf[7];
adts_header(adts_header_buf, pkt.size);
fwrite(adts_header_buf, 1, 7, dst_fd);
// 3:write audio data to aac file
len = fwrite(pkt.data/*待存内容*/, 1/*逐个字节写入*/, pkt.size/*写入多少个字节*/, dst_fd/*写入哪个文件*/);
if(len != pkt.size){
av_log(NULL, AV_LOG_WARNING, "warning, length of data is not equal size of pkt!");
}
}
av_packet_unref(&pkt); // 不管是不是最好的那路流，到这里都要释放
}
avformat_close_input(&fmt_ctx);
if(dst_fd){
fclose(dst_fd);
}
avformat_close_input(&fmt_ctx); // 关闭多媒体文件
return 0;
}
为什么我使用课程中的程序无法成功抽取AAC音频？
利用ffmpeg中的api实现音频抽取
#include <stdio.h>
#include <libavutil/log.h>
#include <libavformat/avio.h>
#include <libavformat/avformat.h>
#define ERROR_STR_SIZE 1024
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 audio_stream_index = -1;
int len;
AVFormatContext *ofmt_ctx = NULL;
AVOutputFormat *output_fmt = NULL;
AVStream *in_stream = NULL;
AVStream *out_stream = NULL;
AVFormatContext *fmt_ctx = NULL;
//AVFrame *frame = 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_DEBUG, "src or dts file is null, plz check them!\n");
return -1;
}
/*register all formats and codec*/
av_register_all();
/*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;
}
/*retrieve audio stream*/
if((err_code = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
av_strerror(err_code, errors, 1024);
av_log(NULL, AV_LOG_DEBUG, "failed to find stream information: %s, %d(%s)\n",
src_filename,
err_code,
errors);
return -1;
}
/*dump input information*/
av_dump_format(fmt_ctx, 0, src_filename, 0);
in_stream = fmt_ctx->streams[1];
AVCodecParameters *in_codecpar = in_stream->codecpar;
if(in_codecpar->codec_type != AVMEDIA_TYPE_AUDIO){
av_log(NULL, AV_LOG_ERROR, "The Codec type is invalid!\n");
exit(1);
}
//out file
ofmt_ctx = avformat_alloc_context();
output_fmt = av_guess_format(NULL, dst_filename, NULL);
if(!output_fmt){
av_log(NULL, AV_LOG_DEBUG, "Cloud not guess file format \n");
exit(1);
}
ofmt_ctx->oformat = output_fmt;
out_stream = avformat_new_stream(ofmt_ctx, NULL);
if(!out_stream){
av_log(NULL, AV_LOG_DEBUG, "Failed to create out stream!\n");
exit(1);
}
if(fmt_ctx->nb_streams<2){
av_log(NULL, AV_LOG_ERROR, "the number of stream is too less!\n");
exit(1);
}
if((err_code = avcodec_parameters_copy(out_stream->codecpar, in_codecpar)) < 0 ){
av_strerror(err_code, errors, ERROR_STR_SIZE);
av_log(NULL, AV_LOG_ERROR,
"Failed to copy codec parameter, %d(%s)\n",
err_code, errors);
}
out_stream->codecpar->codec_tag = 0;
if((err_code = avio_open(&ofmt_ctx->pb, dst_filename, AVIO_FLAG_WRITE)) < 0) {
av_strerror(err_code, errors, 1024);
av_log(NULL, AV_LOG_DEBUG, "Could not open file %s, %d(%s)\n",
dst_filename,
err_code,
errors);
exit(1);
}
/*
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;
}
*/
/*dump output information*/
av_dump_format(ofmt_ctx, 0, dst_filename, 1);
/*
frame = av_frame_alloc();
if(!frame){
av_log(NULL, AV_LOG_DEBUG, "Could not allocate frame\n");
return AVERROR(ENOMEM);
}
*/
/*initialize packet*/
av_init_packet(&pkt);
pkt.data = NULL;
pkt.size = 0;
/*find best audio stream*/
audio_stream_index = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, NULL, 0);
if(audio_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_AUDIO),
src_filename);
return AVERROR(EINVAL);
}
if (avformat_write_header(ofmt_ctx, NULL) < 0) {
av_log(NULL, AV_LOG_DEBUG, "Error occurred when opening output file");
exit(1);
}
/*read frames from media file*/
while(av_read_frame(fmt_ctx, &pkt) >=0 ){
if(pkt.stream_index == audio_stream_index){
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 = pkt.pts;
pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
pkt.pos = -1;
pkt.stream_index = 0;
av_interleaved_write_frame(ofmt_ctx, &pkt);
av_packet_unref(&pkt);
}
}
av_write_trailer(ofmt_ctx);
/*close input media file*/
avformat_close_input(&fmt_ctx);
if(dst_fd) {
fclose(dst_fd);
}
avio_close(ofmt_ctx->pb);
return 0;
}
Start code 在每一帧前面的关键字
将一帧一帧数据区分开：可以在每一帧前面加该帧的长度；也可以在每一帧前面加关键字或特征码；
SPS / PPS 解码的视频帧的参数 每个关键帧前加
codec->extradata 获取SPS和PPS是从编码器的扩展数据中获取，而非从数据包中
目的：
在每一个帧的前面增加Start Code特征码；
在每个关键帧前面增加SPS和PPS，同时也增加了特征码。
avformat_alloc_output_context2() / avformat_free_context()
avformat_new_stream()
avcodec_parameters_copy()
avformat_write_header() 生成多媒体文件头
av_write_frame() / av_interleaved_write_frame()
av_write_trailer()
可以将test.mpt 转换成 test.flv
#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>
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];
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 write_header\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;
}
av_seek_frame()
截取时，./cut 5 15 srcVideo toVideo将视频srcVideo的第5秒到第15秒存入toVideo
#include <stdlib.h>
#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>
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, NULL);
if (!out_stream) {
fprintf(stderr, "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
ret = avcodec_parameters_copy(out_stream->codecpar, in_stream->codecpar);
if (ret < 0) {
fprintf(stderr, "Failed to copy context from input to output stream codec context\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;
}
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_packet_unref(&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;
}
if(pkt.pts < pkt.dts) continue;
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_packet_unref(&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;
}
将两个媒体文件中分别抽取音频与视频
将音频与视频轨合并成一个新文件
对音频与视频轨进行裁剪