I made a program that encodes a video and I want to specify the format as h264 but I can't figure out how to do it. It automatically sets the format to mpeg4 and I can't change it. I got my code from ffmpegs official examples muxing.c and slightly edited it to fit my code (I haven't changed much especially did not touch the parts where it sets the format)
Here is my code so for (I have trimmed down the code slightly, removing redundant parts)
video_encoder.cpp:
video_encoder::video_encoder(int w, int h, float fps, unsigned int duration)
:width(w), height(h), STREAM_FRAME_RATE(fps), STREAM_DURATION(duration)
{
std::string as_str = "./output/video.mp4";
char* filename = const_cast<char*>(as_str.c_str());
enc_inf.video_st, enc_inf.audio_st = (struct OutputStream) { 0 };
enc_inf.video_st.next_pts = 1;
enc_inf.audio_st.next_pts = 1;
enc_inf.encode_audio, enc_inf.encode_video = 0;
int ret;
int i;
/* allocate the output media context */
avformat_alloc_output_context2(&enc_inf.oc, NULL, NULL, filename);
if (!enc_inf.oc) {
std::cout << "FAILED" << std::endl;
avformat_alloc_output_context2(&enc_inf.oc, NULL, "mpeg", filename);
}
enc_inf.fmt = enc_inf.oc->oformat;
/* Add the audio and video streams using the default format codecs
* and initialize the codecs. */
if (enc_inf.fmt->video_codec != AV_CODEC_ID_NONE) {
add_stream(&enc_inf.video_st, enc_inf.oc, &video_codec, enc_inf.fmt->video_codec);
enc_inf.have_video = 1;
enc_inf.encode_video = 1;
}
if (enc_inf.fmt->audio_codec != AV_CODEC_ID_NONE) {
add_stream(&enc_inf.audio_st, enc_inf.oc, &audio_codec, enc_inf.fmt->audio_codec);
enc_inf.have_audio = 1;
enc_inf.encode_audio = 1;
}
/* Now that all the parameters are set, we can open the audio and
* video codecs and allocate the necessary encode buffers. */
if (enc_inf.have_video)
open_video(enc_inf.oc, video_codec, &enc_inf.video_st, opt);
if (enc_inf.have_audio)
open_audio(enc_inf.oc, audio_codec, &enc_inf.audio_st, opt);
av_dump_format(enc_inf.oc, 0, filename, 1);
/* open the output file, if needed */
if (!(enc_inf.fmt->flags & AVFMT_NOFILE)) {
ret = avio_open(&enc_inf.oc->pb, filename, AVIO_FLAG_WRITE);
if (ret < 0) {
//VI_ERROR("Could not open '%s': %s\n", filename, ret);
//return 1;
}
}
/* Write the stream header, if any. */
ret = avformat_write_header(enc_inf.oc, &opt);
if (ret < 0) {
VI_ERROR("Error occurred when opening output file:");
//return 1;
}
//return 0;
}
/* Add an output stream. */
void video_encoder::add_stream(OutputStream *ost, AVFormatContext *oc,
const AVCodec **codec,
enum AVCodecID codec_id)
{
AVCodecContext *c;
int i;
/* find the encoder */
*codec = avcodec_find_encoder(codec_id);
if (!(*codec)) {
fprintf(stderr, "Could not find encoder for '%s'\n",
avcodec_get_name(codec_id));
exit(1);
}
ost->tmp_pkt = av_packet_alloc();
if (!ost->tmp_pkt) {
fprintf(stderr, "Could not allocate AVPacket\n");
exit(1);
}
ost->st = avformat_new_stream(oc, NULL);
if (!ost->st) {
fprintf(stderr, "Could not allocate stream\n");
exit(1);
}
ost->st->id = oc->nb_streams-1;
c = avcodec_alloc_context3(*codec);
if (!c) {
fprintf(stderr, "Could not alloc an encoding context\n");
exit(1);
}
ost->enc = c;
switch ((*codec)->type) {
case AVMEDIA_TYPE_AUDIO:
...
break;
case AVMEDIA_TYPE_VIDEO:
c->codec_id = codec_id;
c->bit_rate = 10000;
/* Resolution must be a multiple of two. */
c->width = width;
c->height = height;
/* timebase: This is the fundamental unit of time (in seconds) in terms
* of which frame timestamps are represented. For fixed-fps content,
* timebase should be 1/framerate and timestamp increments should be
* identical to 1. */
ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE }; // *frame_rate
c->time_base = ost->st->time_base;
c->gop_size = 7; /* emit one intra frame every twelve frames at most */
//c->codec_id = AV_CODEC_ID_H264;
c->pix_fmt = STREAM_PIX_FMT;
//if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO)
// c->max_b_frames = 2;
if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
/* Needed to avoid using macroblocks in which some coeffs overflow.
* This does not happen with normal video, it just happens here as
* the motion of the chroma plane does not match the luma plane. */
c->mb_decision = 2;
}
if ((*codec)->pix_fmts){
//c->pix_fmt = (*codec)->pix_fmts[0];
std::cout << "NEW FORMAT : " << c->pix_fmt << std::endl;
}
break;
}
/* Some formats want stream headers to be separate. */
if (oc->oformat->flags & AVFMT_GLOBALHEADER)
c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}
video_encoder.h
typedef struct OutputStream {
AVStream *st;
AVCodecContext *enc;
/* pts of the next frame that will be generated */
int64_t next_pts;
int samples_count;
AVFrame *frame;
AVFrame *tmp_frame;
AVPacket *tmp_pkt;
float t, tincr, tincr2;
struct SwsContext *sws_ctx;
struct SwrContext *swr_ctx;
} OutputStream;
class video_encoder{
private:
typedef struct {
OutputStream video_st, audio_st;
const AVOutputFormat *fmt;
AVFormatContext *oc;
int have_video, have_audio, encode_video, encode_audio;
std::string name;
} encode_info;
public:
encode_info enc_inf;
video_encoder(int w, int h, float fps, unsigned int duration);
~video_encoder();
...
private:
...
void add_stream(OutputStream *ost, AVFormatContext *oc,
const AVCodec **codec,
enum AVCodecID codec_id);
I'm thinking that the example sets the codec at avformat_alloc_output_context2(&enc_inf.oc, NULL, NULL, filename) but I'm not quite sure how to set it to h264.
I've tried something like this avformat_alloc_output_context2(&enc_inf.oc, enc_inf.fmt, "h264", filename)
But it just gives a seg fault. What am I supposed to do?
Edit: I've tried adding these two lines to video_encoder::video_encoder by deleting avformat_alloc_output_context2(&enc_inf.oc, NULL, NULL, filename);:
video_codec = avcodec_find_encoder(AV_CODEC_ID_H264);
enc_inf.video_st.enc = avcodec_alloc_context3(video_codec);
But it resulted in these errors: It says this every frame (A bunch of times)
[mpeg @ 0x56057c465480] buffer underflow st=0 bufi=26822 size=31816
Says this once when the frame encoding loop is over:
[mpeg @ 0x5565ac4a04c0] start time for stream 0 is not set in estimate_timings_from_pts
[mpeg @ 0x5565ac4a04c0] stream 0 : no TS found at start of file, duration not set
[mpeg @ 0x5565ac4a04c0] Could not find codec parameters for stream 0 (Video: mpeg2video, none): unspecified size
Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options