[Ffmpeg-devel] Re: [PATCH] h264 muxing in mp4

[Michael Niedermayer]

Hi

On Tue, Mar 07, 2006 at 05:40:47PM +0100, Baptiste COUDURIER wrote:
[...]
> 
> >> If anyone see a better or faster way to parse, it would be great.
> > 
> > 
> > 174795 dezicycles in find_startcode_v0 (your algo)
> >  90398 dezicycles in find_startcode_v1
> >  72391 dezicycles in find_startcode_v2 (generic)
> >  69425 dezicycles in find_startcode_v2 (endian)
> 
> Is better, faster this way ?

iam fine with it, if loren has no objections then this can be applied

some comments below, just minor things, nothing important


[...]
> +static void avc_parse_nal_units(uint8_t **buf, int *size)
> +{
> +    ByteIOContext pb;
> +    uint8_t *p = *buf;
> +    uint8_t *end = p + *size;
> +    uint8_t *nal_start, *nal_end;
> +
> +    url_open_dyn_buf(&pb);
> +    nal_start = avc_find_startcode(p, end);

i would change avc_find_startcode so it outputs end instead of NULL if
nothing is found, that way the following code could be simplified like:


> +    while (nal_start) {

while(nal_start < end) {

> +        if (nal_start[2] == 1)
> +            nal_start += 3;
> +        else
> +            nal_start += 4;

somehow my feeling tells me that
while(!*(nal_start++));
would be better but maybe its too hackisch (or even wrong ...)


> +        nal_end = avc_find_startcode(nal_start, end);

> +        if (nal_end) {
> +            put_be32(&pb, nal_end - nal_start);
> +            put_buffer(&pb, nal_start, nal_end - nal_start);
> +        } else {
> +            put_be32(&pb, end - nal_start);
> +            put_buffer(&pb, nal_start, end - nal_start);
> +        }

put_be32(&pb, nal_end - nal_start);
put_buffer(&pb, nal_start, nal_end - nal_start);


[...]

> @@ -1492,6 +1612,31 @@ static int mov_write_packet(AVFormatCont
>          memcpy(trk->vosData, enc->extradata, trk->vosLen);
>      }
>  
> +    if (enc->codec_id == CODEC_ID_H264) {
> +        if (trk->vosLen == 0) {
> +            if (!enc->extradata) {
> +                /* bytestream h264 from avi */
> +                /* will parse frame to get extradata when writing avcc */
> +                /* XXX: parse all frames to get all sps, pps */
> +                trk->vosLen = pkt->size;
> +                trk->vosData = av_malloc(trk->vosLen);
> +                memcpy(trk->vosData, pkt->data, trk->vosLen);

this isnt needed, code which extract global headers from the bitstream
is in the AVParser and is activated by -vglobal 1 on the cmd line

[...]

-- 
Michael