[vlc-devel] [PATCH 4/5] wasapi: add 24bits support

[Steve Lhomme]

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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> 
> -- 
> Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez excuser 
> ma brièveté.
> 
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