X264 : How to access NAL units from encoder?

Question

When I call

frame_size = x264_encoder_encode(encoder, &nals, &i_nals, &pic_in, &pic_out);

and subsequently write each NAL to a file like this:

     if (frame_size >= 0)
     {
        int i;
        int j;

        for (i = 0; i < i_nals; i++)
        {
           printf("******************* NAL %d (%d bytes) *******************\n", i, nals[i].i_payload);
           fwrite(&(nals[i].p_payload[0]), 1, nals[i].i_payload, fid);
        }
     }

then I get this

Beginning of NAL file

My questions are:

1) Is it normal that there's readable parameters in the beginning of the file?

2) How do I configure the X264 encoder so that the encoder returns frames that I can send via UDP without the packet getting fragmented (size must be below 1390 or somewhere around that).

3) With the x264.exe I pass in these options:

"--threads 1 --profile baseline --level 3.2 --preset ultrafast --bframes 0 --force-cfr --no-mbtree --sync-lookahead 0 --rc-lookahead 0 --keyint 1000 --intra-refresh"

How do I map those to the settings in the X264 parameters structure ? (x264_param_t)

4) I have been told that the x264 static library doesn't support bitmap input to the encoder and that I have to use libswscale for conversion of the 24bit RGB input bitmap to YUV2. The encoder, supposedly, only takes YUV2 as input? Is this true? If so, how do I build libswscale for the x264 static library?

szatmary szatmary · Accepted Answer · 2014-04-18T16:15:51

1) Yes. x264 includes the automatically. Its an SEI slice, and you can throw it away if you want.

2) set i_slice_max_size = 1390

3) Take a look at x264_param_t in x264.h. The settings are fairly self explanatory. As for setting the profile and preset call int x264_param_apply_profile( x264_param_t *, const char *profile ) and int x264_param_default_preset( x264_param_t *, const char *preset, const char *tune )

4) Yes, it is true, I want lying when I said that. Look online/on stack overflow there are a million resources on compiling ffmpeg. In fact if you compiled x264 with avcodec support you already have it on your system.

5) Yes!, you should be a good stack overflow citizen and up vote and accept answers form people who donate there free time and knowledge (which takes years to acquire) to helping you.

X264 : How to access NAL units from encoder?

1 Answers