[vlc-devel] [PATCH v2] Reset p_context->skip_frame when done seeking

[Steve Lhomme]

Hi,

On 2019-08-06 5:39, Marc Aldorasi wrote:
> Previously, if p_sys->b_hurry_up was false and we weren't seeking, the
> value of p_context->skip_frame would not be modified.  This means that
> if we started seeking we would set p_context->skip_frame to
> AVDISCARD_NONREF, and then when we finished seeking we wouldn't change
> p_context->skip_frame and it would still be skipping non-reference
> frames, causing choppy playback.  This patch resets
> p_context->skip_frame when we're not seeking so playback is smooth.

The p_context->skip_frame should indeed be reset once seeking is done 
and that's currently not the case if b_hurry_up is false. But it should 
reset it to AVDISCARD_DEFAULT which is the value that is used when 
p_sys->b_hurry_up is false, not the p_sys->i_skip_frame value. Otherwise 
that makes the "avcodec-hurry-up" option useless since it would always 
be applied.

By default the "avcodec-hurry-up" option is true. That means people who 
set it to false really don't want to skip more than non-ref frames.

On the other hand to achieve that they could also use 
--avcodec-skip-frame=1 and it would have the same effect.

So if you want to go that way you should also remove (make obsolete) the 
avcodec-hurry-up option.

By the way, the second part of this test in the current code is useless, 
FRAMEDRO_NONREF is never used/set in the code:

   if( !b_need_output_picture || p_sys->framedrop == FRAMEDROP_NONREF )

> ---
>   modules/codec/avcodec/video.c | 14 ++++++--------
>   1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/modules/codec/avcodec/video.c b/modules/codec/avcodec/video.c
> index 2232b7a291..d9be9d4a61 100644
> --- a/modules/codec/avcodec/video.c
> +++ b/modules/codec/avcodec/video.c
> @@ -1031,15 +1031,13 @@ static int DecodeBlock( decoder_t *p_dec, block_t **pp_block )
>       else
>           b_need_output_picture = false;
>   
> -    /* Change skip_frame config only if hurry_up is enabled */
> -    if( p_sys->b_hurry_up )
> -    {
> -        p_context->skip_frame = p_sys->i_skip_frame;
> +    p_context->skip_frame = p_sys->i_skip_frame;
>   
> -        /* Check also if we should/can drop the block and move to next block
> -            as trying to catchup the speed*/
> -        if( p_dec->b_frame_drop_allowed )
> -            p_block = filter_earlydropped_blocks( p_dec, p_block );
> +    /* Check if we should/can drop the block and move to the next block
> +       to try to catchup */
> +    if( p_sys->b_hurry_up && p_dec->b_frame_drop_allowed )
> +    {
> +        p_block = filter_earlydropped_blocks( p_dec, p_block );
>       }
>   
>       if( !b_need_output_picture || p_sys->framedrop == FRAMEDROP_NONREF )
> -- 
> 2.22.0
> 
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