[MPlayer-dev-eng] [PATCH] Fix playback of 24-bit audio when sndio ao is used

[Brad Smith]

On 04/03/14 2:46 PM, Alexandre Ratchov wrote:
> On Tue, Mar 04, 2014 at 08:05:09PM +0100, Reimar Döffinger wrote:
>>>
>>> --- libao2/ao_sndio.c.orig	Mon Jan  6 23:02:58 2014
>>> +++ libao2/ao_sndio.c	Tue Feb 18 14:31:47 2014
>>> @@ -103,6 +103,8 @@ static int init(int rate, int channels, int format, in
>>>       }
>>>       sio_initpar(&par);
>>>       par.bits = af_fmt2bits(format);
>>> +    par.bps = (par.bits + 7) >> 3;
>>> +    par.msb = 1;
>>
>> This seems kind of questionable, if we had a special format that stored 24 bit in 32 bit
>> it would almost certainly be LSB-aligned.
>> Though I suspect that is related to the next part.
>>
>>> @@ -118,7 +120,7 @@ static int init(int rate, int channels, int format, in
>>>           mp_msg(MSGT_AO, MSGL_ERR, "ao2: couldn't get params\n");
>>>           goto err_out;
>>>       }
>>> -    if (par.bps != SIO_BPS(par.bits)) {
>>> +    if (par.bits < 8 * par.bps && !par.msb) {
>>>           mp_msg(MSGT_AO, MSGL_ERR, "ao2: unsupported format\n");
>>>           goto err_out;
>>>       }
>>
>> I kind of wonder if it isn't a bit overkill to try to make
>> every format work.
>> For most other aos we instead have a fallback to 16 bit/sample
>> signed that is basically supported everywhere instead of
>> giving up right away.
>> It might not pick the ideal format, but better than failing.
>
> This check is kinda "theoretical". On the default setup, there are
> conversion layers that support any linear fixed-point format and
> mplayer never fails.
>
> It will fail if the device picks a unsupported format; this may
> happen if format conversions are disabled (they are enabled by
> default) on a very obscure piece of hardware, like the mavb(4)
> driver which supports only 24-bit LSB-aligned in 32-bit words).
>
>> Unfortunately I also see one last big issue with the code:
>> What happens when the input is float?
>> How does sndio indicated if the input format is float or integer?
>
> It supports integers only.
>
>> It seems that this code will request "32 bit" if the format is
>> float, and when it then gets "32 bit" back it will go ahead
>> and request 32 bit integer from MPlayer, instead of the
>> float it wanted originally...
>
> This is exactly what happens, and this currenly works.

ping.


-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.