[vlc-devel] [PATCH 4/5] wasapi: add 24bits support
Rémi Denis-Courmont
remi at remlab.net
Mon Oct 28 13:47:00 CET 2019
I agree that exclusive mode is necessary. It's the negotiation around it that seems wrong (plus the fact that the resampler is not disabled).
Le 28 octobre 2019 13:41:54 GMT+02:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>On 2019-10-28 11:45, Rémi Denis-Courmont wrote:
>> Hi,
>>
>> Based on the forum requests, I think people want bit exact on
>Windows,
>> not exclusive mode on Thomas Guillem's hardware.
>>
>> Bit exact means no filters, no resampling, no remixing, and no format
>
>> conversion, except maybe exact up-conversion. It does not, as such,
>mean
>> to get audio out with WASAPI exclusive mode.
>
>There's still the OS mixer. If it's bypassed by the exclusive mode,
>that's the only way to really get bit exact output.
>
>> And it makes no sense to duplicate encoder functionality.
>>
>> Le 28 octobre 2019 11:20:40 GMT+02:00, Thomas Guillem
><thomas at gllm.fr> a
>> écrit :
>>
>>
>> On Mon, Oct 28, 2019, at 10:01, Rémi Denis-Courmont wrote:
>>> Hi,
>>>
>>> Patch 4 is triplicating in one aout what belongs in OS HAL and
>VLC
>>> encoders. Are you going to write an MPEG Audio encoder in WASAPI
>>> just because some devices only accept that, also?
>>
>> If users are asking for it, yes, but it won't be top priority at
>all
>> (unless there is huge use case suddenly).
>>
>> I added 24bit support because the first sound card I tested for
>the
>> wasapi exclusive work was only accepting 24bit.
>>
>>>
>>> Patch 5 is doing the opposite of what people want to use
>exclusive
>>> mode for: implicitly add VLC conversion filters instead of
>>> disabling them.
>>
>> OK. Maybe, the "wasapi-exclusive" option should be a global
>option
>> (can be handled by Windows and Mac, don't know for pulse). That
>way,
>> we can disable all audio filtering if enabled.
>>
>> Then, let's say the input is 16bit and the soundcard is 24bit.
>What
>> should we done in that case ? I assumed that it would be always
>OK
>> to convert up to 24bit. Maybe we can add an option to this
>> "exclusive" mode to prevent any conversion.
>>
>>>
>>> I don't think either of them is a step in the right direction.
>>>
>>> Le 28 octobre 2019 10:25:02 GMT+02:00, Thomas Guillem
>>> <thomas at gllm.fr> a écrit :
>>>
>>>
>>> On Fri, Oct 25, 2019, at 18:15, Rémi Denis-Courmont wrote:
>>>
>>> Le perjantaina 25. lokakuuta 2019, 15.45.16 EEST
>Alexandre
>>> Janniaux a écrit :
>>>
>>> Hi,
>>>
>>> To be honest, when the main answer is "it was
>decided
>>> decades ago", I do feel it's a great secret wisdom.
>>>
>>> That's not what I wrote, and that just means it's
>obvious
>>> enough that there's
>>> no point reopening the topic.
>>>
>>> Thomas's patch seems to make sense though, as a lot
>of
>>> audio softwares are implementing it. There are also
>>> probably some different use cases for exclusive mode
>when
>>> using VLC in a different use case than the home
>multimedia
>>> player.
>>>
>>> I don't see how the patchset is useful. I've seen
>requests
>>> for PCM pass-
>>> through, which sort-of makes sense with a digital
>output,
>>> but that's not at
>>> all what this patchset does.
>>>
>>> PCM pass-through means that you set exclusive mode and
>>> force the DAC format to
>>> match the sample rate, channel map of the decoded input,
>>> and pick the wire
>>> sample format, practically signed 16-bits. This patch
>does
>>> almost the exact
>>> opposite: negotiate the rate, map and bit depth.
>>>
>>>
>>> My patch is good step toward this direction.
>>> It will first try the input format, but fallback to other
>>> possible compatible format. We can use a 3 value options:
>>> disabled, FORCED, ON if format compatible.
>>> The main problem is that VLC can insert audio-filter like
>time
>>> stretch that could alterate the audio/format.
>>>
>>> >
>>>
>>> --
>>> Реми Дёни-Курмон
>>> http://www.remlab.net/
>>>
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>>
>>
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>> ma brièveté.
>>
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