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

[Thomas Guillem]

On Thu, Oct 24, 2019, at 18:29, Rémi Denis-Courmont wrote:
> So what? Some cards don't support PCM at all, or only some really weird formats. That's why we use the OS-provided HAL.

In that case, we can also add support for such format.

Yes, we must use the OS-provided HAL by default. But we can still add an advanced option to enable exclusive mode. I know a lot of audiophile would like to play their 24bit 96khz directly. Even if I know that 16bit 48khz cover fully the hearing range.

> 
> I don't think this belongs in VLC. We already decided to drop 24-bits PCM earlier.

Who ? when ? Do you have a trace ?

> 
> Le 24 octobre 2019 15:37:12 GMT+03:00, Thomas Guillem <thomas at gllm.fr> a écrit :
>> But don't use VLC_CODEC_S24N as this fourcc is not handled by any audio
>> filters. Instead, request VLC_CODEC_S32N to VLC and do the conversion
>> internally.
>> 
>> This commit is needed by the next commit since some sound cards only support
>> 24bits. modules/audio_output/wasapi.c | 30 +++++++++++++++++++++++++++---
>>  1 file changed, 27 insertions(+), 3 deletions(-)
>> 
>> diff --git a/modules/audio_output/wasapi.c b/modules/audio_output/wasapi.c
>> index d6105169b8e..daa946f8afc 100644
>> --- a/modules/audio_output/wasapi.c
>> +++ b/modules/audio_output/wasapi.c
>> @@ -106,6 +106,7 @@ typedef struct aout_stream_sys
>>      unsigned block_align;
>>      UINT64 written; /**< Frames written to the buffer */
>>      UINT32 frames; /**< Total buffer size (frames) */
>> +    bool s24s32; /**< Output configured as S24N, but input as S32N */
>>  } aout_stream_sys_t;
>>  
>>  static void ResetTimer(aout_stream_t *s)
>> @@ -268,7 +269,28 @@ static HRESULT Play(aout_stream_t *s, block_t *block, vlc_tick_t date)
>>  
>>          const size_t copy = frames * sys->block_align;
>>  
>> -        memcpy(dst, block->p_buffer, copy);
>> +        if (!sys->s24s32)
>> +        {
>> +            memcpy(dst, block->p_buffer, copy);
>> +            block->p_buffer += copy;
>> +            block->i_buffer -= copy;
>> +        }
>> +        else
>> +        {
>> +            /* Convert back S32L to S24L. The following is doing the opposite
>> +             * of S24LDecode() from codec/araw.c */
>> +            BYTE *end = dst + copy;
>> +            while (dst < end)
>> +            {
>> +                dst[0] = block->p_buffer[1];
>> +                dst[1] = block->p_buffer[2];
>> +                dst[2] = block->p_buffer[3];
>> +                dst += 3;
>> +                block->p_buffer += 4;
>> +                block->i_buffer -= 4;
>> +            }
>> +
>> +        }
>>          hr = IAudioRenderClient_ReleaseBuffer(render, frames, 0);
>>          if (FAILED(hr))
>>          {
>> @@ -276,8 +298,6 @@ static HRESULT Play(aout_stream_t *s, block_t *block, vlc_tick_t date)
>>              break;
>>          }
>>  
>> -        block->p_buffer += copy;
>> -        block->i_buffer -= copy;
>>          block->i_nb_samples -= frames;
>>          sys->written += frames;
>>          if (block->i_nb_samples == 0)
>> @@ -512,6 +532,7 @@ static int vlc_FromWave(const WAVEFORMATEX *restrict wf,
>>              switch (wf->wBitsPerSample)
>>              {
>>                  case 32:
>> +                case 24:
>>                      audio->i_format = VLC_CODEC_S32N;
>>                      break;
>>                  case 16:
>> @@ -679,6 +700,9 @@ static HRESULT Start(aout_stream_t *s, audio_sample_format_t *restrict pfmt,
>>      sys->format = fmt.i_format;
>>      sys->block_align = pwf->nBlockAlign;
>>      sys->rate = pwf->nSamplesPerSec;
>> +    sys->s24s32 = pwf->wBitsPerSample == 24 && fmt.i_format == VLC_CODEC_S32N;
>> +    if (sys->s24s32)
>> +        msg_Dbg(s, "audio device configured as s24");
>>  
>>      hr = IAudioClient_Initialize(sys->client, shared_mode, 0, buffer_duration,
>>                                   0, pwf, sid);
> 
> -- 
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