[FFmpeg-devel] [PATCH] avcodec/hevc_ps: improve check for missing default display window bitstream

[James Almer]

On 9/11/2017 7:52 PM, Michael Niedermayer wrote:
> On Thu, Sep 07, 2017 at 09:49:54PM -0300, James Almer wrote:
>> Fixes ticket #6644
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>  libavcodec/hevc_ps.c | 33 +++++++++++++++++++++++++++------
>>  1 file changed, 27 insertions(+), 6 deletions(-)
>>
>> diff --git a/libavcodec/hevc_ps.c b/libavcodec/hevc_ps.c
>> index ee31cc093c..eb104ca1b9 100644
>> --- a/libavcodec/hevc_ps.c
>> +++ b/libavcodec/hevc_ps.c
>> @@ -550,7 +550,7 @@ err:
>>  static void decode_vui(GetBitContext *gb, AVCodecContext *avctx,
>>                         int apply_defdispwin, HEVCSPS *sps)
>>  {
>> -    VUI *vui          = &sps->vui;
>> +    VUI backup_vui, *vui = &sps->vui;
>>      GetBitContext backup;
>>      int sar_present, alt = 0;
>>  
>> @@ -618,13 +618,14 @@ static void decode_vui(GetBitContext *gb, AVCodecContext *avctx,
>>      vui->field_seq_flag                = get_bits1(gb);
>>      vui->frame_field_info_present_flag = get_bits1(gb);
>>  
>> +    // Backup context in case an alternate header is detected
>> +    memcpy(&backup, gb, sizeof(backup));
>> +    memcpy(&backup_vui, vui, sizeof(backup_vui));
>>      if (get_bits_left(gb) >= 68 && show_bits_long(gb, 21) == 0x100000) {
>>          vui->default_display_window_flag = 0;
>>          av_log(avctx, AV_LOG_WARNING, "Invalid default display window\n");
>>      } else
>>          vui->default_display_window_flag = get_bits1(gb);
>> -    // Backup context in case an alternate header is detected
>> -    memcpy(&backup, gb, sizeof(backup));
>>  
>>      if (vui->default_display_window_flag) {
>>          int vert_mult  = 1 + (sps->chroma_format_idc < 2);
>> @@ -651,18 +652,19 @@ static void decode_vui(GetBitContext *gb, AVCodecContext *avctx,
>>          }
>>      }
>>  
>> +timing_info:
>>      vui->vui_timing_info_present_flag = get_bits1(gb);
>>  
>>      if (vui->vui_timing_info_present_flag) {
>> -        if( get_bits_left(gb) < 66) {
>> +        if( get_bits_left(gb) < 66 && !alt) {
>>              // The alternate syntax seem to have timing info located
>>              // at where def_disp_win is normally located
>>              av_log(avctx, AV_LOG_WARNING,
>>                     "Strange VUI timing information, retrying...\n");
>> -            vui->default_display_window_flag = 0;
>> -            memset(&vui->def_disp_win, 0, sizeof(vui->def_disp_win));
>> +            memcpy(vui, &backup_vui, sizeof(backup_vui));
>>              memcpy(gb, &backup, sizeof(backup));
>>              alt = 1;
>> +            goto timing_info;
>>          }
>>          vui->vui_num_units_in_tick               = get_bits_long(gb, 32);
>>          vui->vui_time_scale                      = get_bits_long(gb, 32);
>> @@ -680,6 +682,15 @@ static void decode_vui(GetBitContext *gb, AVCodecContext *avctx,
>>  
>>      vui->bitstream_restriction_flag = get_bits1(gb);
>>      if (vui->bitstream_restriction_flag) {
>> +        if (get_bits_left(gb) < 8 && !alt) {
>> +            av_log(avctx, AV_LOG_WARNING,
>> +                   "Strange VUI bitstream restriction information, retrying"
>> +                   " from timing information...\n");
>> +            memcpy(vui, &backup_vui, sizeof(backup_vui));
>> +            memcpy(gb, &backup, sizeof(backup));
>> +            alt = 1;
>> +            goto timing_info;
>> +        }
>>          vui->tiles_fixed_structure_flag              = get_bits1(gb);
>>          vui->motion_vectors_over_pic_boundaries_flag = get_bits1(gb);
>>          vui->restricted_ref_pic_lists_flag           = get_bits1(gb);
>> @@ -689,6 +700,16 @@ static void decode_vui(GetBitContext *gb, AVCodecContext *avctx,
>>          vui->log2_max_mv_length_horizontal           = get_ue_golomb_long(gb);
>>          vui->log2_max_mv_length_vertical             = get_ue_golomb_long(gb);
>>      }
>> +
>> +    if (get_bits_left(gb) < 1 && !alt) {
>> +        // XXX: Alternate syntax when sps_range_extension_flag != 0?
>> +        av_log(avctx, AV_LOG_WARNING,
>> +               "Overread in VUI, retrying from timing information...\n");
>> +        memcpy(vui, &backup_vui, sizeof(backup_vui));
>> +        memcpy(gb, &backup, sizeof(backup));
>> +        alt = 1;
>> +        goto timing_info;
>> +    }
>>  }
> 
> the duplicated code is a bit ugly, but the change itself should be ok
> 
> thanks

Pushed, thanks.