Prepare
ffmepeg 4.4
A H264 video file
An audio file in acc format
Packaging process
1. Use avformat_open_input to open the video and audio files respectively, initialize its AVFormatContext, and use avformat_find_stream_info to obtain the basic information of the encoder
2. Use avformat_alloc_output_context2 to initialize the output AVFormatContext structure
3. Use the function avformat_new_stream to create audio and video streams for the output AVFormatContext structure, and use the avcodec_parameters_copy method to copy the encoding parameters of the audio and video to the codecpar structure of the newly created corresponding stream
4. Use avio_open to open the output file and initialize the IO context structure in the output AVFormatContext structure
5. Use avformat_write_header to write the header information of the stream to the output file
6. Write audio and video data interleaved according to the time stamp synchronization principle, and set and calibrate the time stamp information
7. Write stream preview information to the output file (moov)
8. Free up space and close the file
source code
#include <stdio.h>
#define __STDC_CONSTANT_MACROS
#ifdef _WIN32
//Windows
extern "C"
{
#include "libavformat/avformat.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavformat/avformat.h>
#ifdef __cplusplus
};
#endif
#endif
int main(int argc, char* argv[]) {
AVOutputFormat* ofmt = NULL;
//Input AVFormatContext and Output AVFormatContext
AVFormatContext* ifmt_ctx_v = NULL, * ifmt_ctx_a = NULL, * ofmt_ctx = NULL;
AVPacket pkt;
int ret, i;
int videoindex_v = -1, videoindex_out = -1;
int audioindex_a = -1, audioindex_out = -1;
int frame_index = 0;
int64_t cur_pts_v = 0, cur_pts_a = 0;
int writing_v = 1, writing_a = 1;
const char* in_filename_v = "D:/测试工程/sound/ffmpeg_demo.h264";
const char* in_filename_a = "D:/测试工程/sound/ffmpeg_demo.aac";
const char* out_filename = "D:/测试工程/sound/muxing.mp4";//Output file URL
if ((ret = avformat_open_input(&ifmt_ctx_v, in_filename_v, 0, 0)) < 0) {
printf("Could not open input file.");
goto end;
}
if ((ret = avformat_find_stream_info(ifmt_ctx_v, 0)) < 0) {
printf("Failed to retrieve input stream information");
goto end;
}
if ((ret = avformat_open_input(&ifmt_ctx_a, in_filename_a, 0, 0)) < 0) {
printf("Could not open input file.");
goto end;
}
if ((ret = avformat_find_stream_info(ifmt_ctx_a, 0)) < 0) {
printf("Failed to retrieve input stream information");
goto end;
}
//Output
avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
if (!ofmt_ctx) {
printf("Could not create output context\n");
ret = AVERROR_UNKNOWN;
goto end;
}
ofmt = ofmt_ctx->oformat;
for (i = 0; i < ifmt_ctx_v->nb_streams; i++) {
//Create output AVStream according to input AVStream
if (ifmt_ctx_v->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
AVStream* out_stream = avformat_new_stream(ofmt_ctx, nullptr);
videoindex_v = i;
if (!out_stream) {
printf("Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
videoindex_out = out_stream->index;
//Copy the settings of AVCodecContext
if (avcodec_parameters_copy(out_stream->codecpar, ifmt_ctx_v->streams[i]->codecpar) < 0) {
printf("Failed to copy context from input to output stream codec context\n");
goto end;
}
break;
}
}
for (i = 0; i < ifmt_ctx_a->nb_streams; i++) {
//Create output AVStream according to input AVStream
if (ifmt_ctx_a->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
AVStream* out_stream = avformat_new_stream(ofmt_ctx, nullptr);
audioindex_a = i;
if (!out_stream) {
printf("Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
audioindex_out = out_stream->index;
//Copy the settings of AVCodecContext
if (avcodec_parameters_copy(out_stream->codecpar, ifmt_ctx_a->streams[i]->codecpar) < 0) {
printf("Failed to copy context from input to output stream codec context\n");
goto end;
}
out_stream->codecpar->codec_tag = 0;
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
ofmt_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
break;
}
}
/* open the output file, if needed */
if (!(ofmt->flags & AVFMT_NOFILE)) {
if (avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE)) {
fprintf(stderr, "Could not open '%s': %d\n", out_filename,
ret);
goto end;
}
}
//Write file header
if (avformat_write_header(ofmt_ctx, NULL) < 0) {
fprintf(stderr, "Error occurred when opening output file: %d\n",
ret);
goto end;
}
//写入数据
while (writing_v || writing_a)
{
AVFormatContext* ifmt_ctx;
int stream_index = 0;
AVStream* in_stream, * out_stream;
if (writing_v &&
(!writing_a || av_compare_ts(cur_pts_v, ifmt_ctx_v->streams[videoindex_v]->time_base,
cur_pts_a, ifmt_ctx_a->streams[audioindex_a]->time_base) <= 0))
{
ifmt_ctx = ifmt_ctx_v;
stream_index = videoindex_out;
if (av_read_frame(ifmt_ctx, &pkt) >= 0)
{
do {
in_stream = ifmt_ctx->streams[pkt.stream_index];
out_stream = ofmt_ctx->streams[stream_index];
if (pkt.stream_index == videoindex_v)
{
//FIX：No PTS (Example: Raw H.264)
//Simple Write PTS
if (pkt.pts == AV_NOPTS_VALUE)
{
//Write PTS
AVRational time_base1 = in_stream->time_base;
//Duration between 2 frames (us)
int64_t calc_duration = (double)AV_TIME_BASE / av_q2d(in_stream->r_frame_rate);
//Parameters
pkt.pts = (double)(frame_index * calc_duration) / (double)(av_q2d(time_base1) * AV_TIME_BASE);
pkt.dts = pkt.pts;
pkt.duration = (double)calc_duration / (double)(av_q2d(time_base1) * AV_TIME_BASE);
frame_index++;
printf("frame_index: %d\n ", frame_index);
}
cur_pts_v = pkt.pts;
break;
}
} while
(av_read_frame(ifmt_ctx, &pkt) >= 0);
}
else
{
writing_v = 0;
continue;
}
}
else
{
ifmt_ctx = ifmt_ctx_a;
stream_index = audioindex_out;
if (av_read_frame(ifmt_ctx, &pkt) >= 0)
{
do {
in_stream = ifmt_ctx->streams[pkt.stream_index];
out_stream = ofmt_ctx->streams[stream_index];
if (pkt.stream_index == audioindex_a)
{
//FIX：No PTS
//Simple Write PTS
if (pkt.pts == AV_NOPTS_VALUE)
{
//Write PTS
AVRational time_base1 = in_stream->time_base;
//Duration between 2 frames (us)
int64_t calc_duration = (double)AV_TIME_BASE / av_q2d(in_stream->r_frame_rate);
//Parameters
pkt.pts = (double)(frame_index * calc_duration) /
(double)(av_q2d(time_base1) * AV_TIME_BASE);
pkt.dts = pkt.pts;
pkt.duration = (double)calc_duration / (double)(av_q2d(time_base1) * AV_TIME_BASE);
frame_index++;
}
cur_pts_a = pkt.pts;
break;
}
} while (av_read_frame(ifmt_ctx, &pkt) >= 0);
}
else
{
writing_a = 0;
continue;
}
}
//Convert PTS/DTS
pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base,
(AVRounding)(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;
pkt.stream_index = stream_index;
printf("Write 1 Packet. size:%5d\tpts:%lld\n", pkt.size, pkt.pts);
//Write
if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0) {
printf("Error muxing packet\n");
break;
}
av_packet_unref(&pkt);
}
printf("Write file trailer.\n");
//Write file trailer
av_write_trailer(ofmt_ctx);
end:
avformat_close_input(&ifmt_ctx_v);
avformat_close_input(&ifmt_ctx_a);
/* close output */
if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
avio_close(ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
if (ret < 0 && ret != AVERROR_EOF) {
printf("Error occurred.\n");
return -1;
}
return 0;
}summary
A few concepts need to be briefly explained here:
tbr means frames per second
tbn represents the reciprocal of the actual real frame rate of the data stream
like: