[vlc-devel] [PATCH] mux: mp4: handle both short and long NALU startcodes (fix #14185)

[Jean-Baptiste Kempf]

LGTM.

On 17 Mar, Francois Cartegnie wrote :
> AnnexB packets were truncated by 1 bytes on conversion if starting with 
> 3 bytes start code. (SEI/Comment)
> 
> Since hevc in mp4 seems broken before that, I can't tell if it would break
> (not same sync codes).
> 
> Realloc on the fly won't be optimal in case of frequent 3 bytes start codes.
> 
> Francois
> 
> ---
>  modules/mux/mp4.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 48 insertions(+), 5 deletions(-)
> 
> diff --git a/modules/mux/mp4.c b/modules/mux/mp4.c
> index 566074b..447e088 100644
> --- a/modules/mux/mp4.c
> +++ b/modules/mux/mp4.c
> @@ -231,6 +231,7 @@ static bo_t *GetMoovBox(sout_mux_t *p_mux);
>  static block_t *ConvertSUBT(block_t *);
>  static block_t *ConvertFromAnnexB(block_t *);
>  
> +static const char avc1_short_start_code[3] = { 0, 0, 1 };
>  static const char avc1_start_code[4] = { 0, 0, 0, 1 };
>  
>  /*****************************************************************************
> @@ -751,24 +752,66 @@ static block_t *ConvertSUBT(block_t *p_block)
>  
>  static block_t *ConvertFromAnnexB(block_t *p_block)
>  {
> -    uint8_t *last = p_block->p_buffer;  /* Assume it starts with 0x00000001 */
> +    if(p_block->i_buffer < 4)
> +    {
> +        block_Release(p_block);
> +        return NULL;
> +    }
> +
> +    if(memcmp(p_block->p_buffer, avc1_start_code, 4))
> +    {
> +        if(!memcmp(p_block->p_buffer, avc1_short_start_code, 3))
> +        {
> +            p_block = block_Realloc(p_block, 1, p_block->i_buffer);
> +            if( !p_block )
> +                return NULL;
> +        }
> +        else /* No startcode on start */
> +        {
> +            block_Release(p_block);
> +            return NULL;
> +        }
> +    }
> +
> +    uint8_t *last = p_block->p_buffer;
>      uint8_t *dat  = &p_block->p_buffer[4];
>      uint8_t *end = &p_block->p_buffer[p_block->i_buffer];
>  
> -
> -    /* Replace the 4 bytes start code with 4 bytes size,
> -     * FIXME are all startcodes 4 bytes ? (I don't think :(*/
> +    /* Replace the 4 bytes start code with 4 bytes size */
>      while (dat < end) {
>          while (dat < end - 4) {
>              if (!memcmp(dat, avc1_start_code, 4))
> +            {
>                  break;
> +            }
> +            else if(!memcmp(dat, avc1_short_start_code, 3))
> +            {
> +                /* save offsets as we don't know if realloc will replace buffer */
> +                size_t i_last = last - p_block->p_buffer;
> +                size_t i_dat = dat - p_block->p_buffer;
> +                size_t i_end = end - p_block->p_buffer;
> +
> +                p_block = block_Realloc(p_block, 0, p_block->i_buffer + 1);
> +                if( !p_block )
> +                    return NULL;
> +
> +                /* restore offsets */
> +                last = &p_block->p_buffer[i_last];
> +                dat = &p_block->p_buffer[i_dat];
> +                end = &p_block->p_buffer[i_end];
> +
> +                /* Shift data */
> +                memmove(&dat[4], &dat[3], end - &dat[3]);
> +                end++;
> +                break;
> +            }
>              dat++;
>          }
>          if (dat >= end - 4)
>              dat = end;
>  
>          /* Fix size */
> -        int i_size = dat - &last[4];
> +        uint32_t i_size = dat - &last[4];
>          SetDWBE((uint32_t*) last, i_size);
>  
>          /* Skip blocks with SPS/PPS */
> -- 
> 2.1.0
> 
> _______________________________________________
> vlc-devel mailing list
> To unsubscribe or modify your subscription options:
> https://mailman.videolan.org/listinfo/vlc-devel

-- 
With my kindest regards,

-- 
Jean-Baptiste Kempf
http://www.jbkempf.com/ - +33 672 704 734
Sent from my Electronic Device