Using Libavformat to convert native H 264 file to a container format (mp4)

Question

I have been working on the encoding_decoding.c example provided along with ffmpeg to encode data using different codecs (specifically x264) as a part of an experiment. The output the function video_encode_example provides is a native h264 file. Here is a snapshot of the code:

AVCodec *codec;
AVCodecContext *c= NULL;
int i, out_size, x, y, outbuf_size;
FILE *f;
AVFrame *picture;
uint8_t *outbuf;
int had_output=0;
struct AVRational av = { 1, 25 };

printf("Encode video file %s\n", filename);

/* find the mpeg1 video encoder */
codec = avcodec_find_encoder( ( enum CodecID )codec_id);
if (!codec) {
    fprintf(stderr, "codec not found\n");
    exit(1);
}

c = avcodec_alloc_context3(codec);
picture= avcodec_alloc_frame();

/* put sample parameters */
c->bit_rate = 400000;
/* resolution must be a multiple of two */
c->width = 352;
c->height = 288;
/* frames per second */
//
c->time_base= av;
c->gop_size = 10; /* emit one intra frame every ten frames */
c->max_b_frames=1;
c->pix_fmt = PIX_FMT_YUV420P;

if(codec_id == CODEC_ID_H264)
    av_opt_set(c->priv_data, "preset", "slow", 0);

/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
    fprintf(stderr, "could not open codec\n");
    exit(1);
}

f = fopen(filename, "wb");
if (!f) {
    fprintf(stderr, "could not open %s\n", filename);
    exit(1);
}

/* alloc image and output buffer */
outbuf_size = 100000 + 12*c->width*c->height;
outbuf = (uint8_t *) malloc(outbuf_size);

/* the image can be allocated by any means and av_image_alloc() is
 * just the most convenient way if av_malloc() is to be used */
av_image_alloc(picture->data, picture->linesize,
               c->width, c->height, c->pix_fmt, 1);

/* encode 1 second of video */
for(i=0;i<25;i++) {
    fflush(stdout);
    /* prepare a dummy image */
    /* Y */
    for(y=0;y<c->height;y++) {
        for(x=0;x<c->width;x++) {
            picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
        }
    }

    /* Cb and Cr */
    for(y=0;y<c->height/2;y++) {
        for(x=0;x<c->width/2;x++) {
            picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
            picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
        }
    }

    /* encode the image */
    out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
    had_output |= out_size;
    printf("encoding frame %3d (size=%5d)\n", i, out_size);
    fwrite(outbuf, 1, out_size, f);
}

/* get the delayed frames */
for(; out_size || !had_output; i++) {
    fflush(stdout);

    out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
    had_output |= out_size;
    printf("write frame %3d (size=%5d)\n", i, out_size);
    fwrite(outbuf, 1, out_size, f);
}

/* add sequence end code to have a real mpeg file */
outbuf[0] = 0x00;
outbuf[1] = 0x00;
outbuf[2] = 0x01;
outbuf[3] = 0xb7;
fwrite(outbuf, 1, 4, f);
fclose(f);
free(outbuf);

avcodec_close(c);
av_free(c);
av_free(picture->data[0]);
av_free(picture);
printf("\n");  

Now, i would like an mp4 file as the output. I know i need to use the libavformat library for the same but i am unable to find out the exact details/functions. Any help/pointers on any tutorial or a small code snippet would really be helpful.

Answer 1

 ffmpeg\doc\examples\muxing.c

This sample save 264 to .mp4

int main(int argc, char **argv)
{
  filename = argv[1]; //output.mp4 OK

}