Re: [FFmpeg-devel] [PATCH 1/3] avcodec/avs3_parser: set has_b_frames properly

["\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com>]

> On May 13, 2022, at 5:43 PM, Andreas Rheinhardt <andreas.rheinhardt@outlook.com> wrote:
> 
> Zhao Zhili:
>> has_b_frames should be output_reorder_delay field in AVS3 sequence
>> header and larger than 1. The parser implementation doesn't parse
>> that field. Decoder can set has_b_frames properly, so use FFMAX
>> here to avoid resetting has_b_frames from output_reorder_delay to 1.
>> ---
>> libavcodec/avs3_parser.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/libavcodec/avs3_parser.c b/libavcodec/avs3_parser.c
>> index d04d96a03a..0d2e940d1e 100644
>> --- a/libavcodec/avs3_parser.c
>> +++ b/libavcodec/avs3_parser.c
>> @@ -114,7 +114,7 @@ static void parse_avs3_nal_units(AVCodecParserContext *s, const uint8_t *buf,
>>             //            bitrate_high(12)
>>             skip_bits(&gb, 32);
>> 
>> -            avctx->has_b_frames = !get_bits(&gb, 1);
>> +            avctx->has_b_frames = FFMAX(avctx->has_b_frames, !get_bits(&gb, 1));
>> 
>>             avctx->framerate.num = avctx->time_base.den = ff_avs3_frame_rate_tab[ratecode].num;
>>             avctx->framerate.den = avctx->time_base.num = ff_avs3_frame_rate_tab[ratecode].den;
> 
> FFMAX can evaluate its arguments more than once which is not intended here.

Good catch, thanks! Here is v2:
http://ffmpeg.org/pipermail/ffmpeg-devel/2022-May/296396.html

Use a variable low_delay to fix the FFMAX issue and serve as document.

> 
> - Andreas
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