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

Submitted by Andriy Gelman on Sept. 21, 2019, 1:57 a.m.

Details

Message ID 20190921015715.24769-1-andriy.gelman@gmail.com
State New
Headers show

Commit Message

Andriy Gelman Sept. 21, 2019, 1:57 a.m.
From: Andriy Gelman <andriy.gelman@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(-)

Comments

Carl Eugen Hoyos Sept. 21, 2019, 10:44 p.m.
Am Sa., 21. Sept. 2019 um 04:06 Uhr schrieb Andriy Gelman
<andriy.gelman@gmail.com>:
>
> From: Andriy Gelman <andriy.gelman@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
Andriy Gelman Sept. 22, 2019, 4:28 a.m.
On Sun, 22. Sep 00:44, Carl Eugen Hoyos wrote:
> Am Sa., 21. Sept. 2019 um 04:06 Uhr schrieb Andriy Gelman
> <andriy.gelman@gmail.com>:
> >
> > From: Andriy Gelman <andriy.gelman@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.

ok, I removed and sent updated version.

Thanks,

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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
 
     if (vps_list && !vps_list[sps->vps_id]) {
         av_log(avctx, AV_LOG_ERROR, "VPS %d does not exist\n",