x264 encoded frames into a mp4 container with ffmpeg API - ffmpeg

Question

I'm struggling with understanding what is and what is not needed in getting my already encoded x264 frames into a video container file using ffmpeg's libavformat API.
My current program will get the x264 frames like this -
while( x264_encoder_delayed_frames( h ) )
{
printf("Writing delayed frame %u\n", delayed_frame_counter++);
i_frame_size = x264_encoder_encode( h, &nal, &i_nal, NULL, &pic_out );
if( i_frame_size < 0 ) {
printf("Failed to encode a delayed x264 frame.\n");
return ERROR;
}
else if( i_frame_size )
{
if( !fwrite(nal->p_payload, i_frame_size, 1, video_file_ptr) ) {
printf("Failed to write a delayed x264 frame.\n");
return ERROR;
}
}
}
If I use the CLI to the ffmpeg binary, I can put these frames into a container using:
ffmpeg -i "raw_frames.h264" -c:v copy -f mp4 "video.mp4"
I would like to code this function into my program using the libavformat API though. I'm a little stuck in the concepts and the order on which each ffmpeg function is needed to be called.
So far I have written:
mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
printf("Guessed format\n");
int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
printf("Created context = %d\n", ret);
printf("Format = %s\n", mAVFormatContext->oformat->name);
mAVStream = avformat_new_stream(mAVFormatContext, 0);
if (!mAVStream) {
printf("Failed allocating output stream\n");
} else {
printf("Allocated stream.\n");
}
mAVCodecParameters = mAVStream->codecpar;
if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
printf("Invalid codec?\n");
}
if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
if (ret < 0) {
printf("Could not open output file '%s'", "gen_vid.mp4");
}
}
ret = avformat_write_header(mAVFormatContext, NULL);
if (ret < 0) {
printf("Error occurred when opening output file\n");
}
This will print out:
Guessed format
Created context = 0
Format = mp4
Allocated stream.
Invalid codec?
[mp4 # 0x55ffcea2a2c0] Could not find tag for codec none in stream #0, codec not currently supported in container
Error occurred when opening output file
How can I make sure the codec type is set correctly for my video?
Next I need to somehow point my mAVStream to use my x264 frames - advice would be great.
Update 1:
So I've tried to set the H264 codec, so the codec's meta-data is available. I seem to hit 2 newer issues now.
1) It cannot find the device and therefore cannot configure the encoder.
2) I get the "dimensions not set".
mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
printf("Guessed format\n");
// MUST allocate the media file format context.
int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
printf("Created context = %d\n", ret);
printf("Format = %s\n", mAVFormatContext->oformat->name);
// Even though we already have encoded the H264 frames using x264,
// we still need the codec's meta-data.
const AVCodec *mAVCodec;
mAVCodec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!mAVCodec) {
fprintf(stderr, "Codec '%s' not found\n", "H264");
exit(1);
}
mAVCodecContext = avcodec_alloc_context3(mAVCodec);
if (!mAVCodecContext) {
fprintf(stderr, "Could not allocate video codec context\n");
exit(1);
}
printf("Codec context allocated with defaults.\n");
/* put sample parameters */
mAVCodecContext->bit_rate = 400000;
mAVCodecContext->width = width;
mAVCodecContext->height = height;
mAVCodecContext->time_base = (AVRational){1, 30};
mAVCodecContext->framerate = (AVRational){30, 1};
mAVCodecContext->gop_size = 10;
mAVCodecContext->level = 31;
mAVCodecContext->max_b_frames = 1;
mAVCodecContext->pix_fmt = AV_PIX_FMT_NV12;
av_opt_set(mAVCodecContext->priv_data, "preset", "slow", 0);
printf("Set codec parameters.\n");
// Initialize the AVCodecContext to use the given AVCodec.
avcodec_open2(mAVCodecContext, mAVCodec, NULL);
// Add a new stream to a media file. Must be called before
// calling avformat_write_header().
mAVStream = avformat_new_stream(mAVFormatContext, mAVCodec);
if (!mAVStream) {
printf("Failed allocating output stream\n");
} else {
printf("Allocated stream.\n");
}
// TODO How should codecpar be set?
mAVCodecParameters = mAVStream->codecpar;
if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
printf("Invalid codec?\n");
}
if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
if (ret < 0) {
printf("Could not open output file '%s'", "gen_vid.mp4");
}
}
printf("Called avio_open()\n");
// MUST write a header.
ret = avformat_write_header(mAVFormatContext, NULL);
if (ret < 0) {
printf("Error occurred when opening output file (writing header).\n");
}
Now I am getting this output -
Guessed format
Created context = 0
Format = mp4
Codec context allocated with defaults.
Set codec parameters.
[h264_v4l2m2m # 0x556460344b40] Could not find a valid device
[h264_v4l2m2m # 0x556460344b40] can't configure encoder
Allocated stream.
Invalid codec?
Called avio_open()
[mp4 # 0x5564603442c0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
[mp4 # 0x5564603442c0] dimensions not set
Error occurred when opening output file (writing header).