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

[Hendrik Leppkes]

On Sat, Mar 26, 2016 at 10:38 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> index 2d447f7..170db31 100644
> --- a/libavcodec/h264_mp4toannexb_bsf.c
> +++ b/libavcodec/h264_mp4toannexb_bsf.c
> @@ -167,7 +167,8 @@ static int h264_mp4toannexb_filter(AVBitStreamFilterContext *bsfc,
>      int ret = 0;
>
>      /* 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.

- Hendrik