Re: [FFmpeg-devel] [PATCH] avcodec/hevc_ps: allocate only the required HEVCHdrParams within a VPS

["Wu, Tong1" <tong1.wu-at-intel.com@ffmpeg.org>]

Hi James,

>From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of James
>Almer
>Sent: Thursday, March 21, 2024 8:29 PM
>To: ffmpeg-devel@ffmpeg.org
>Subject: [FFmpeg-devel] [PATCH] avcodec/hevc_ps: allocate only the required
>HEVCHdrParams within a VPS
>
>Signed-off-by: James Almer <jamrial@gmail.com>
>---
> libavcodec/hevc_ps.c | 14 +++++++++++++-
> libavcodec/hevc_ps.h |  2 +-
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
>diff --git a/libavcodec/hevc_ps.c b/libavcodec/hevc_ps.c
>index fb997066d9..d29cf9f372 100644
>--- a/libavcodec/hevc_ps.c
>+++ b/libavcodec/hevc_ps.c
>@@ -438,13 +438,20 @@ static int decode_hrd(GetBitContext *gb, int
>common_inf_present,
>     return 0;
> }
>
>+static void uninit_vps(FFRefStructOpaque opaque, void *obj)
>+{
>+    HEVCVPS *vps = obj;
>+
>+    av_freep(&vps->hdr);
>+}
>+
> int ff_hevc_decode_nal_vps(GetBitContext *gb, AVCodecContext *avctx,
>                            HEVCParamSets *ps)
> {
>     int i,j;
>     int vps_id = 0;
>     ptrdiff_t nal_size;
>-    HEVCVPS *vps = ff_refstruct_allocz(sizeof(*vps));
>+    HEVCVPS *vps = ff_refstruct_alloc_ext(sizeof(*vps), 0, NULL, uninit_vps);
>
>     if (!vps)
>         return AVERROR(ENOMEM);
>@@ -533,6 +540,11 @@ int ff_hevc_decode_nal_vps(GetBitContext *gb,
>AVCodecContext *avctx,
>                    "vps_num_hrd_parameters %d is invalid\n", vps-
>>vps_num_hrd_parameters);
>             goto err;
>         }
>+
>+        vps->hdr = av_calloc(vps->vps_num_hrd_parameters, sizeof(*vps->hdr));
>+        if (!vps->hdr)
>+            goto err;
>+

It looks like this will cause the following !memcmp(ps->vps_list[vps_id], vps, sizeof(*vps)) becomes 0 and furtherly remove_vps is called. Is that expected?

Thanks,
Tong


>         for (i = 0; i < vps->vps_num_hrd_parameters; i++) {
>             int common_inf_present = 1;
>
>diff --git a/libavcodec/hevc_ps.h b/libavcodec/hevc_ps.h
>index 786c896709..87cea479e9 100644
>--- a/libavcodec/hevc_ps.h
>+++ b/libavcodec/hevc_ps.h
>@@ -152,7 +152,7 @@ typedef struct PTL {
>
> typedef struct HEVCVPS {
>     unsigned int vps_id;
>-    HEVCHdrParams hdr[HEVC_MAX_LAYER_SETS];
>+    HEVCHdrParams *hdr;
>
>     uint8_t vps_temporal_id_nesting_flag;
>     int vps_max_layers;
>--
>2.44.0
>
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