我正在尝试将多个文件中的所有流复制到一个文件中而不转码流。通常由ffmpeg
ffmpeg -i “file_with_audio.mp4” -i “file_with_video.mp4” -c copy -shortest file_with_audio_and_video.mp4实用程序执行的操作
这是代码：
int ffmpegOpenInputFile(const char* filename, AVFormatContext **ic) {
int ret;
unsigned int i;
*ic = avformat_alloc_context();
if (!(*ic))
return -1; // Couldn't allocate input context
if((ret = avformat_open_input(ic, filename, NULL, NULL)) < 0)
return ret; // Couldn't open file
// Get format info (retrieve stream information)
if ((ret = avformat_find_stream_info(*ic, NULL)) < 0)
return ret; // Couldn't find stream information
for (int i = 0; i < (*ic)->nb_streams; i++) {
AVStream *stream;
AVCodecContext *codec_ctx;
stream = (*ic)->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;
}
}
}
// Dump information about file onto standard error
av_dump_format(*ic, 0, filename, 0);
return 0;
}
int main(int argc, char *argv[]) {
const char *inputFilename1 = "/avfiles/video_input.mp4";
const char *inputFilename2 = "/avfiles/audio_input.mp4";
const char *filename = "/avfiles/out.mp4";
int ret;
av_register_all();
AVFormatContext *ic1 = nullptr;
AVFormatContext *ic2 = nullptr;
AVFormatContext *oc = nullptr;
if ((ret = ffmpegOpenInputFile(inputFilename1, &ic1)) < 0)
return ret; // and free resources and
if ((ret = ffmpegOpenInputFile(inputFilename2, &ic2)) < 0)
return ret; // and free resources and
AVOutputFormat *outfmt = av_guess_format(NULL, filename, NULL);
if (outfmt == NULL)
return -1; // Could not guess output format
avformat_alloc_output_context2(&oc, outfmt, NULL, filename);
if (!oc)
return AVERROR_UNKNOWN; // Could not create output context
// populate input streams from all input files
AVStream **input_streams = NULL;
int nb_input_streams = 0;
for (int i = 0; i < ic1->nb_streams; i++) {
input_streams = (AVStream **) grow_array(input_streams, sizeof(*input_streams), &nb_input_streams,
nb_input_streams + 1);
input_streams[nb_input_streams - 1] = ic1->streams[i];
}
for (int i = 0; i < ic2->nb_streams; i++) {
input_streams = (AVStream **) grow_array(input_streams, sizeof(*input_streams), &nb_input_streams,
nb_input_streams + 1);
input_streams[nb_input_streams - 1] = ic2->streams[i];
}
for (int i = 0; i < nb_input_streams; i++) {
AVStream *ist = input_streams[i]; // could be named 'm_in_vid_strm'
// if output context has video codec support and current input stream is video
if (/*oc->video_codec_id*/ oc->oformat->video_codec != AV_CODEC_ID_NONE && ist != NULL
&& ist->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
AVCodec *out_vid_codec = avcodec_find_encoder(oc->oformat->video_codec);
if (NULL == out_vid_codec)
return -1; // Couldn't find video encoder
AVStream *m_out_vid_strm = avformat_new_stream(oc, out_vid_codec);
if (NULL == m_out_vid_strm)
return -1; // Couldn't output video stream
m_out_vid_strm->id = 0; // XXX:
ret = avcodec_copy_context(m_out_vid_strm->codec, ist->codec);
if (ret < 0)
return ret; // Failed to copy context
}
// if output context has audio codec support and current input stream is audio
if (/*oc->audio_codec_id*/ oc->oformat->audio_codec != AV_CODEC_ID_NONE && ist != NULL
&& ist->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
AVCodec *out_aud_codec = avcodec_find_encoder(oc->oformat->audio_codec);
if (nullptr == out_aud_codec)
return -1; // couldn't find audio codec
AVStream *m_out_aud_strm = avformat_new_stream(oc, out_aud_codec);
if (nullptr == m_out_aud_strm)
return -1; // couldn't allocate audio out stream
ret = avcodec_copy_context(m_out_aud_strm->codec, ist->codec);
if (ret < 0)
return ret; // couldn't copy context
}
}
// finally output header
if (!(oc->flags & AVFMT_NOFILE)) {
ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
if (ret < 0)
return ret; // Could not open output file
av_dump_format(oc, 0, filename, 1);
ret = avformat_write_header(oc, NULL);
if (ret < 0)
return ret; // Error occurred when opening output file
}
return 0;
}
avformat_write_header(oc, NULL);总是返回错误，我看到了这样的消息：
[mp4 @ 0x7f84ec900a00] Using AVStream.codec.time_base as a timebase hint to the muxer is deprecated. Set AVStream.time_base instead.
[mp4 @ 0x7f84ec900a00] Tag avc1/0x31637661 incompatible with output codec id '28' ([33][0][0][0])
但输入和输出流匹配：
Input streams from 2 files:
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 2834 kb/s, 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc (default)
Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s (default)
Output #0, mp4, to '/Users/alex/Workspace/_qt/tubisto/avfiles/out.mp4':
Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 2834 kb/s, 47.95 tbc
Stream #0:1: Audio: aac (libvo_aacenc) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s
为什么输出编解码器不兼容的错误发生？ 我的代码有什么问题，以及如何将所有输入文件中的所有流复制到输出文件？
答案 0 :(得分：3)
原因是您没有正确设置编码器的codec_tag。
您应该设置正确的codec_tag，或将codec_tag设置为0并让复制器为您处理。
以下是示例代码。
AVFormatContext *ofmt_ctx; // todo
AVCodec *oc; // todo
AVStream *stream = avformat_new_stream(ofmt_ctx, oc);
if (stream != NULL) {
// ...
unsigned int tag = 0;
// for ffmpeg new api 3.x
AVCodecParameters *parameters = stream->codecpar;
if (av_codec_get_tag2(ofmt_ctx->oformat->codec_tag, oc->id, &tag) == 0) {
av_log(NULL, AV_LOG_ERROR, "could not find codec tag for codec id %d, default to 0.\n", oc->id);
}
parameters->codec_tag = tag;
stream->codec = avcodec_alloc_context3(oc);
// more setting for stream->codec
avcodec_parameters_to_context(stream->codec, parameters);
// for old ffmpeg version
stream->codec->codec_tag = tag;
// ...
}