Re: [FFmpeg-devel] [PATCH] avocdec/hevc_ps: don't use a fixed sized buffer for parameter set raw data

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

James Almer:
> Allocate it instead, and use it to compare sets instead of the parsed struct.
> 
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
>  libavcodec/hevc_ps.c | 84 ++++++++++++++++++++++----------------------
>  libavcodec/hevc_ps.h | 14 +++++---
>  2 files changed, 51 insertions(+), 47 deletions(-)
> 
> diff --git a/libavcodec/hevc_ps.c b/libavcodec/hevc_ps.c
> index 6475d86d7d..e417039d76 100644
> --- a/libavcodec/hevc_ps.c
> +++ b/libavcodec/hevc_ps.c
> @@ -442,20 +442,18 @@ static int decode_hrd(GetBitContext *gb, int common_inf_present,
>      return 0;
>  }
>  
> -static void uninit_vps(FFRefStructOpaque opaque, void *obj)
> +static void hevc_vps_free(FFRefStructOpaque opaque, void *obj)
>  {
>      HEVCVPS *vps = obj;
>  
>      av_freep(&vps->hdr);
> +    av_freep(&vps->data);
>  }
>  
>  static int compare_vps(const HEVCVPS *vps1, const HEVCVPS *vps2)
>  {
> -    if (!memcmp(vps1, vps2, offsetof(HEVCVPS, hdr)))
> -        return !vps1->vps_num_hrd_parameters ||
> -               !memcmp(vps1->hdr, vps2->hdr, vps1->vps_num_hrd_parameters * sizeof(*vps1->hdr));
> -
> -    return 0;
> +    return vps1->data_size == vps2->data_size &&
> +           !memcmp(vps1->data, vps2->data, vps1->data_size);
>  }
>  
>  int ff_hevc_decode_nal_vps(GetBitContext *gb, AVCodecContext *avctx,
> @@ -463,25 +461,20 @@ int ff_hevc_decode_nal_vps(GetBitContext *gb, AVCodecContext *avctx,
>  {
>      int i,j;
>      int vps_id = 0;
> -    ptrdiff_t nal_size;
> -    HEVCVPS *vps = ff_refstruct_alloc_ext(sizeof(*vps), 0, NULL, uninit_vps);
> +    int ret = AVERROR_INVALIDDATA;
> +    HEVCVPS *vps = ff_refstruct_alloc_ext(sizeof(*vps), 0, NULL, hevc_vps_free);
>  
>      if (!vps)
>          return AVERROR(ENOMEM);
>  
>      av_log(avctx, AV_LOG_DEBUG, "Decoding VPS\n");
>  
> -    nal_size = gb->buffer_end - gb->buffer;
> -    if (nal_size > sizeof(vps->data)) {
> -        av_log(avctx, AV_LOG_WARNING, "Truncating likely oversized VPS "
> -               "(%"PTRDIFF_SPECIFIER" > %"SIZE_SPECIFIER")\n",
> -               nal_size, sizeof(vps->data));
> -        vps->data_size = sizeof(vps->data);
> -    } else {
> -        vps->data_size = nal_size;
> +    vps->data_size = gb->buffer_end - gb->buffer;
> +    vps->data = av_memdup(gb->buffer, vps->data_size);
> +    if (!vps->data) {
> +        ret = AVERROR(ENOMEM);
> +        goto err;
>      }
> -    memcpy(vps->data, gb->buffer, vps->data_size);
> -
>      vps_id = vps->vps_id = get_bits(gb, 4);
>  
>      if (get_bits(gb, 2) != 3) { // vps_reserved_three_2bits
> @@ -591,7 +584,7 @@ int ff_hevc_decode_nal_vps(GetBitContext *gb, AVCodecContext *avctx,
>  
>  err:
>      ff_refstruct_unref(&vps);
> -    return AVERROR_INVALIDDATA;
> +    return ret;
>  }
>  
>  static void decode_vui(GetBitContext *gb, AVCodecContext *avctx,
> @@ -1294,36 +1287,43 @@ int ff_hevc_parse_sps(HEVCSPS *sps, GetBitContext *gb, unsigned int *sps_id,
>      return 0;
>  }
>  
> +static void hevc_sps_free(FFRefStructOpaque opaque, void *obj)
> +{
> +    HEVCSPS *sps = obj;
> +
> +    av_freep(&sps->data);
> +}
> +
> +static int compare_sps(const HEVCSPS *sps1, const HEVCSPS *sps2)
> +{
> +    return sps1->data_size == sps2->data_size &&
> +           !memcmp(sps1->data, sps2->data, sps1->data_size);
> +}
> +
>  int ff_hevc_decode_nal_sps(GetBitContext *gb, AVCodecContext *avctx,
>                             HEVCParamSets *ps, int apply_defdispwin)
>  {
> -    HEVCSPS *sps = ff_refstruct_allocz(sizeof(*sps));
> +    HEVCSPS *sps = ff_refstruct_alloc_ext(sizeof(*sps), 0, NULL, hevc_sps_free);
>      unsigned int sps_id;
>      int ret;
> -    ptrdiff_t nal_size;
>  
>      if (!sps)
>          return AVERROR(ENOMEM);
>  
>      av_log(avctx, AV_LOG_DEBUG, "Decoding SPS\n");
>  
> -    nal_size = gb->buffer_end - gb->buffer;
> -    if (nal_size > sizeof(sps->data)) {
> -        av_log(avctx, AV_LOG_WARNING, "Truncating likely oversized SPS "
> -               "(%"PTRDIFF_SPECIFIER" > %"SIZE_SPECIFIER")\n",
> -               nal_size, sizeof(sps->data));
> -        sps->data_size = sizeof(sps->data);
> -    } else {
> -        sps->data_size = nal_size;
> +    sps->data_size = gb->buffer_end - gb->buffer;
> +    sps->data = av_memdup(gb->buffer, sps->data_size);
> +    if (!sps->data) {
> +        ret = AVERROR(ENOMEM);
> +        goto err;
>      }
> -    memcpy(sps->data, gb->buffer, sps->data_size);
>  
>      ret = ff_hevc_parse_sps(sps, gb, &sps_id,
>                              apply_defdispwin,
>                              ps->vps_list, avctx);
>      if (ret < 0) {
> -        ff_refstruct_unref(&sps);
> -        return ret;
> +        goto err;
>      }
>  
>      if (avctx->debug & FF_DEBUG_BITSTREAM) {
> @@ -1340,7 +1340,7 @@ int ff_hevc_decode_nal_sps(GetBitContext *gb, AVCodecContext *avctx,
>       * original one.
>       * otherwise drop all PPSes that depend on it */
>      if (ps->sps_list[sps_id] &&
> -        !memcmp(ps->sps_list[sps_id], sps, sizeof(*sps))) {
> +        compare_sps(ps->sps_list[sps_id], sps)) {
>          ff_refstruct_unref(&sps);
>      } else {
>          remove_sps(ps, sps_id);
> @@ -1348,6 +1348,9 @@ int ff_hevc_decode_nal_sps(GetBitContext *gb, AVCodecContext *avctx,
>      }
>  
>      return 0;
> +err:
> +    ff_refstruct_unref(&sps);
> +    return ret;
>  }
>  
>  static void hevc_pps_free(FFRefStructOpaque unused, void *obj)
> @@ -1364,6 +1367,7 @@ static void hevc_pps_free(FFRefStructOpaque unused, void *obj)
>      av_freep(&pps->tile_pos_rs);
>      av_freep(&pps->tile_id);
>      av_freep(&pps->min_tb_addr_zs_tab);
> +    av_freep(&pps->data);
>  }
>  
>  static void colour_mapping_octants(GetBitContext *gb, HEVCPPS *pps, int inp_depth,
> @@ -1773,16 +1777,12 @@ int ff_hevc_decode_nal_pps(GetBitContext *gb, AVCodecContext *avctx,
>  
>      av_log(avctx, AV_LOG_DEBUG, "Decoding PPS\n");
>  
> -    nal_size = gb->buffer_end - gb->buffer;
> -    if (nal_size > sizeof(pps->data)) {
> -        av_log(avctx, AV_LOG_WARNING, "Truncating likely oversized PPS "
> -               "(%"PTRDIFF_SPECIFIER" > %"SIZE_SPECIFIER")\n",
> -               nal_size, sizeof(pps->data));
> -        pps->data_size = sizeof(pps->data);
> -    } else {
> -        pps->data_size = nal_size;
> +    pps->data_size = gb->buffer_end - gb->buffer;
> +    pps->data = av_memdup(gb->buffer, pps->data_size);
> +    if (!pps->data) {
> +        ret = AVERROR_INVALIDDATA;
> +        goto err;
>      }
> -    memcpy(pps->data, gb->buffer, pps->data_size);
>  
>      // Default values
>      pps->loop_filter_across_tiles_enabled_flag = 1;
> diff --git a/libavcodec/hevc_ps.h b/libavcodec/hevc_ps.h
> index 0d8eaf2b3e..bed406770f 100644
> --- a/libavcodec/hevc_ps.h
> +++ b/libavcodec/hevc_ps.h
> @@ -172,11 +172,11 @@ typedef struct HEVCVPS {
>      int vps_num_ticks_poc_diff_one; ///< vps_num_ticks_poc_diff_one_minus1 + 1
>      int vps_num_hrd_parameters;
>  
> -    uint8_t data[4096];
> -    int data_size;
> -    /* Put this at the end of the structure to make it easier to calculate the
> +    /* Keep this at the end of the structure to make it easier to calculate the
>       * size before this pointer, which is used for memcmp */
>      HEVCHdrParams *hdr;
> +    uint8_t *data;
> +    int data_size;
>  } HEVCVPS;
>  
>  typedef struct ScalingList {
> @@ -299,7 +299,9 @@ typedef struct HEVCSPS {
>  
>      int qp_bd_offset;
>  
> -    uint8_t data[4096];
> +    /* Keep this at the end of the structure to make it easier to calculate the
> +     * size before this pointer, which is used for memcmp */
> +    uint8_t *data;
>      int data_size;
>  } HEVCSPS;
>  
> @@ -434,7 +436,9 @@ typedef struct HEVCPPS {
>      int *min_tb_addr_zs;    ///< MinTbAddrZS
>      int *min_tb_addr_zs_tab;///< MinTbAddrZS
>  
> -    uint8_t data[4096];
> +    /* Keep this at the end of the structure to make it easier to calculate the
> +     * size before this pointer, which is used for memcmp */
> +    uint8_t *data;
>      int data_size;
>  } HEVCPPS;
>  

This is vastly overcomplicated: If you already have the complete data of
the earlier PS, all you need is comparing the data before you even parse
the new parameter set.

- Andreas

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