[vlc-devel] [PATCH 3/6] clock: add vlc_clock_SetDecoderLatency

[Rémi Denis-Courmont]

As far as I can tell, this makes broken assumptions that will break playback in some cases.

Le 3 octobre 2019 10:37:52 GMT+03:00, Thomas Guillem <thomas at gllm.fr> a écrit :
>Any last words ?
>
>On Tue, Oct 1, 2019, at 14:33, Thomas Guillem wrote:
>> 
>> 
>> On Mon, Sep 30, 2019, at 21:52, Rémi Denis-Courmont wrote:
>> > Le torstaina 26. syyskuuta 2019, 17.38.11 EEST Thomas Guillem a
>écrit :
>> > > The highest decoder latency of all clocks will be used to setup
>the initial
>> > > dejitter delay.
>> > 
>> > We cannot generally, or even usually, measure the decoder latency.
>> 
>> I agree, but we the avcodec module can guess it, according to its 
>> thread_count and fps. It's not perfect but it's sufficient to fix all
>
>> problems we have with low fps samples (when you have a CPU with lot
>of 
>> cores).
>> 
>> > 
>> > On top of that, even if we could measure it, it does not even seem
>to mean 
>> > anything if the set of active ES changes, or if for any reason the
>ES are not 
>> > in sync (input slaves, multiple RTP sessions, etc).
>> 
>> Yes, this is why this function can fail.
>vlc_clock_SetDecoderLatency() 
>> won't be able to handle a big delay ( > 300ms = file-caching) if a 
>> video track is enabled midstream. Everything is handled in avcodec:
>> cf. 
>>
>https://code.videolan.org/tguillem/vlc/commit/38206d600fe2eba78a72cc4b19749db087b6a408
>> 
>> This is not a perfect solution but it will fix most issues we have
>with 
>> normal media samples (video starting near the audio).
>> 
>> > 
>> > -- 
>> > レミ・デニ-クールモン
>> > http://www.remlab.net/
>> > 
>> > 
>> > 
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