[FFmpeg-devel] [PATCH]lavc/h264_mp4toannexb: Do not fail if frame already starts with startcode

[Carl Eugen Hoyos]

Hendrik Leppkes <h.leppkes <at> gmail.com> writes:

> On Sat, Mar 26, 2016 at 10:38 AM, Carl Eugen Hoyos wrote:

> >   /* nothing to filter */
> > - if (!avctx->extradata || avctx->extradata_size < 6) {
> > + if (   !avctx->extradata || avctx->extradata_size < 6
> > +     || !buf[0] && !buf[1] && (buf[2] == 1 || !buf[2] && buf[3] == 1)) {
> >       *poutbuf      = (uint8_t *)buf;
> >       *poutbuf_size = buf_size;
> >       return 0;
> 
> A 4-byte mp4 style size code could conceivably start with 0x000001xx
> (ie. a size from 256 bytes to 511 bytes), this seems very risky.

Understood.
Is it ok to test for 32bit "1"?
ie:
|| !buf[0] && !buf[1] && !buf[2] && buf[3] == 1)

Carl Eugen