[FFmpeg-devel] [PATCH] avcodec/hevc_ps: Remove dead code in vps_id check

[Carl Eugen Hoyos]

Am Sa., 21. Sept. 2019 um 04:06 Uhr schrieb Andriy Gelman
<andriy.gelman at gmail.com>:
>
> From: Andriy Gelman <andriy.gelman at gmail.com>
>
> Since reading 4 bits always returns a value in the range [0, 15], the
> check for vps_id >= HEVC_MAX_VPS_COUNT, where HEVC_MAX_VPS_COUNT = 16, is redudant.
> ---
>  libavcodec/hevc_ps.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/libavcodec/hevc_ps.c b/libavcodec/hevc_ps.c
> index abf08b919b..498467730b 100644
> --- a/libavcodec/hevc_ps.c
> +++ b/libavcodec/hevc_ps.c
> @@ -447,11 +447,7 @@ int ff_hevc_decode_nal_vps(GetBitContext *gb, AVCodecContext *avctx,
>      }
>      memcpy(vps->data, gb->buffer, vps->data_size);
>
> -    vps_id = get_bits(gb, 4);
> -    if (vps_id >= HEVC_MAX_VPS_COUNT) {
> -        av_log(avctx, AV_LOG_ERROR, "VPS id out of range: %d\n", vps_id);
> -        goto err;
> -    }
> +    vps_id = get_bits(gb, 4); // vps_id in [0, HEVC_MAX_VPS_COUNT-1] so no check needed
>
>      if (get_bits(gb, 2) != 3) { // vps_reserved_three_2bits
>          av_log(avctx, AV_LOG_ERROR, "vps_reserved_three_2bits is not three\n");
> @@ -882,11 +878,7 @@ int ff_hevc_parse_sps(HEVCSPS *sps, GetBitContext *gb, unsigned int *sps_id,
>
>      // Coded parameters
>
> -    sps->vps_id = get_bits(gb, 4);
> -    if (sps->vps_id >= HEVC_MAX_VPS_COUNT) {
> -        av_log(avctx, AV_LOG_ERROR, "VPS id out of range: %d\n", sps->vps_id);
> -        return AVERROR_INVALIDDATA;
> -    }
> +    sps->vps_id = get_bits(gb, 4); // sps->vps_id in [0, HEVC_MAX_VPS_COUNT-1] so no check needed

The comments look unneeded.

Carl Eugen