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

[Steve Lhomme]

On 2019-08-20 3:26, Marc Aldorasi wrote:
> On Mon, Aug 19, 2019 at 8:39 AM Steve Lhomme <robux4 at ycbcr.xyz> wrote:
>>
>> 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.
> 
> I'm a bit confused by this.  In response to the last patch you wrote
> 
>> It's a good idea to reset the skip_frame once seeking is done, but it
>> should revert to "p_sys->i_skip_frame" so that it respects the
>> "avcodec-skip-frame" variable.
> 
> which I took to mean that it should always be respecting
> avcodec-skip-frame.  If I follow the latest suggestion, I'm concerned it
> contradicts the previous suggestion.
> 
>> 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.
> 
> The avcodec-hurry-up option still guards the call to
> filter_earlydropped_blocks, so I'd prefer not to go that way.

Ah yes, I missed that part. So never mind, we still keep both options. 
We just need to reset properly p_context->skip_frame in both modes then.

>> 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 )
> 
> Good catch, I'll remove that.
> 
>>> ---
>>>    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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