Re: [PATCH 06/23] sdlaudio: fill remaining sample buffer with silence

["Volker Rümelin" <vr_qemu@t-online.de>]

> On 10/01/2021 11.02, Volker Rümelin wrote:
>> Fill the remaining sample buffer with silence. To fill it with
>> zeroes is wrong for unsigned samples because this is silence
>> with a DC bias.
>>
>> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
>> ---
>>   audio/sdlaudio.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/audio/sdlaudio.c b/audio/sdlaudio.c
>> index 79eed23849..01ae4c600e 100644
>> --- a/audio/sdlaudio.c
>> +++ b/audio/sdlaudio.c
>> @@ -235,7 +235,8 @@ static void sdl_callback (void *opaque, Uint8 
>> *buf, int len)
>>         /* clear remaining buffer that we couldn't fill with data */
>>       if (len) {
>> -        memset(buf, 0, len);
>> +        audio_pcm_info_clear_buf(&hw->info, buf,
>> +                                 len / hw->info.bytes_per_frame);
>>       }
>>   }
>>
>
> Ignorant question: Is anybody still using unsigned samples in the 21st 
> century?
>

Hi Thomas,

you are probably right that no one is knowingly using unsigned samples 
anymore. But qemu emulates audio devices from the last century. For 
example with the command line options -machine pcspk-audiodev=audio0 
-audiodev sdl,id=audio0,out.buffer-length=3750,out.mixing-engine=off you 
will see 8 bit unsigned samples in the SDL callback buffer.

With best regards,
Volker

> Anyway,
> Reviewed-by: Thomas Huth <thuth@redhat.com>
>