[FFmpeg-devel] [PATCH 2/3 v2] avcodec/aacdec_template: add more checks to make sure only 22.2 gets to 22.2

[Michael Niedermayer]

On Sat, Aug 22, 2020 at 12:57:59AM +0300, Jan Ekström wrote:
> This way we can check that we have exactly the required things for 22.2.
> 
> Fixes #8845
> ---
>  libavcodec/aacdec_template.c | 47 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 45 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/aacdec_template.c b/libavcodec/aacdec_template.c
> index 9f7016790e..63604d39fd 100644
> --- a/libavcodec/aacdec_template.c
> +++ b/libavcodec/aacdec_template.c
> @@ -266,6 +266,7 @@ static int count_paired_channels(uint8_t (*layout_map)[3], int tags, int pos,
>      return num_pos_channels;
>  }
>  
> +#define PREFIX_FOR_22POINT2 (AV_CH_LAYOUT_7POINT1_WIDE_BACK|AV_CH_BACK_CENTER|AV_CH_SIDE_LEFT|AV_CH_SIDE_RIGHT|AV_CH_LOW_FREQUENCY_2)
>  static uint64_t sniff_channel_order(uint8_t (*layout_map)[3], int tags)
>  {
>      int i, n, total_non_cc_elements;
> @@ -402,46 +403,86 @@ static uint64_t sniff_channel_order(uint8_t (*layout_map)[3], int tags)
>      }
>  
>      // The previous checks would end up at 8 at this point for 22.2
> -    if (tags == 16 && i == 8) {
> +    if (layout == PREFIX_FOR_22POINT2 && tags == 16 && i == 8) {
> +        if (layout_map[i][0] != TYPE_SCE ||
> +            layout_map[i][2] != AAC_CHANNEL_FRONT)
> +            goto end_of_layout_definition;
> +
>          e2c_vec[i] = (struct elem_to_channel) {
>              .av_position  = AV_CH_TOP_FRONT_CENTER,
>              .syn_ele      = layout_map[i][0],
>              .elem_id      = layout_map[i][1],
>              .aac_position = layout_map[i][2]
>          }; layout |= e2c_vec[i].av_position; i++;
> +
> +        if (layout_map[i][0] != TYPE_CPE ||
> +            layout_map[i][2] != AAC_CHANNEL_FRONT)
> +            goto end_of_layout_definition;
> +
>          i += assign_pair(e2c_vec, layout_map, i,
>                           AV_CH_TOP_FRONT_LEFT,
>                           AV_CH_TOP_FRONT_RIGHT,
>                           AAC_CHANNEL_FRONT,
>                           &layout);
> +
> +        if (layout_map[i][0] != TYPE_CPE ||
> +            layout_map[i][2] != AAC_CHANNEL_SIDE)
> +            goto end_of_layout_definition;
> +
>          i += assign_pair(e2c_vec, layout_map, i,
>                           AV_CH_TOP_SIDE_LEFT,
>                           AV_CH_TOP_SIDE_RIGHT,
>                           AAC_CHANNEL_SIDE,
>                           &layout);
> +
> +        if (layout_map[i][0] != TYPE_SCE ||
> +            layout_map[i][2] != AAC_CHANNEL_FRONT)
> +            goto end_of_layout_definition;
> +
>          e2c_vec[i] = (struct elem_to_channel) {
>              .av_position  = AV_CH_TOP_CENTER,
>              .syn_ele      = layout_map[i][0],
>              .elem_id      = layout_map[i][1],
>              .aac_position = layout_map[i][2]
>          }; layout |= e2c_vec[i].av_position; i++;
> +
> +        if (layout_map[i][0] != TYPE_CPE ||
> +            layout_map[i][2] != AAC_CHANNEL_BACK)
> +            goto end_of_layout_definition;
> +
>          i += assign_pair(e2c_vec, layout_map, i,
>                           AV_CH_TOP_BACK_LEFT,
>                           AV_CH_TOP_BACK_RIGHT,
>                           AAC_CHANNEL_BACK,
>                           &layout);
> +
> +        if (layout_map[i][0] != TYPE_SCE ||
> +            layout_map[i][2] != AAC_CHANNEL_BACK)
> +            goto end_of_layout_definition;
> +
>          e2c_vec[i] = (struct elem_to_channel) {
>              .av_position  = AV_CH_TOP_BACK_CENTER,
>              .syn_ele      = layout_map[i][0],
>              .elem_id      = layout_map[i][1],
>              .aac_position = layout_map[i][2]
>          }; layout |= e2c_vec[i].av_position; i++;
> +
> +
> +        if (layout_map[i][0] != TYPE_SCE ||
> +            layout_map[i][2] != AAC_CHANNEL_FRONT)
> +            goto end_of_layout_definition;
> +
>          e2c_vec[i] = (struct elem_to_channel) {
>              .av_position  = AV_CH_BOTTOM_FRONT_CENTER,
>              .syn_ele      = layout_map[i][0],
>              .elem_id      = layout_map[i][1],
>              .aac_position = layout_map[i][2]
>          }; layout |= e2c_vec[i].av_position; i++;
> +
> +        if (layout_map[i][0] != TYPE_CPE ||
> +            layout_map[i][2] != AAC_CHANNEL_FRONT)
> +            goto end_of_layout_definition;
> +
>          i += assign_pair(e2c_vec, layout_map, i,
>                           AV_CH_BOTTOM_FRONT_LEFT,
>                           AV_CH_BOTTOM_FRONT_RIGHT,
> @@ -449,9 +490,11 @@ static uint64_t sniff_channel_order(uint8_t (*layout_map)[3], int tags)
>                           &layout);
>      }
>  
> +end_of_layout_definition:
> +
>      total_non_cc_elements = n = i;

Probably ok if you intend for partial matches to be accepted partially,
because i think this would accept whatever comes before a mismatch but
not after, but maybe iam missing something

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If the United States is serious about tackling the national security threats 
related to an insecure 5G network, it needs to rethink the extent to which it
values corporate profits and government espionage over security.-Bruce Schneier
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