[FFmpeg-devel] patch for DCA "floating point output" option

[Måns Rullgård]

madshi <dear at madshi.net> writes:

> M?ns Rullg?rd schrieb:
>> madshi <dear at madshi.net> writes:
>>
>>   
>>> M?ns Rullg?rd schrieb:
>>>     
>>>> madshi <dear at madshi.net> writes:
>>>>
>>>>   
>>>>       
>>>>> Not sure whether the DCA maintainers will like this patch. But maybe
>>>>> they will, so I'm posting it here just in case.
>>>>>
>>>>> This patch adds optional floating point output to the DCA
>>>>> decoder. This optional feature must be enabled at compile time by
>>>>> adding the following switch to config.h:
>>>>>
>>>>> #define CONFIG_AUDIO_NONSHORT 1
>>>>>
>>>>> I'm using this solution in my eac3to tool because 16bit PCM just
>>>>> doesn't cut it for a good audio transcoding tool. The idea for this
>>>>> option comes from the MLP/TrueHD decoder which offers a similar
>>>>> feature.
>>>>>
>>>>> +#ifdef CONFIG_AUDIO_NONSHORT
>>>>>     
>>>>>         
>>>> That's a rather useless name.  Can't you think of anything better?
>>>>
>>>>   
>>>>       
>>> It was not my idea. The same constant is already used by the
>>> MLP/TrueHD decoder. I thought that it doesn't make sense to
>>> use a different name for every decoder...
>>>
>>> Besides, I don't think that the name is useless. Currently the decoders
>>> all output "short" samples (shorter than they should be). "non short"
>>> simply means that the decoders stop shorten the audio samples.
>>>     
>>
>> The name is equally non-descriptive for any decoder.  If the output is
>> not 'short', then what is it?
>>   
>
> Well, the point of the constant is to allow the decoder to output
> whatever sample format suits best. It may be floating point or
> 24 bit integer or even the usual 16 bit integer. Of course the
> decoder must set the "sample_fmt" field to the correct value.
> My patch does that. The MLP/TrueHD decoder does that, too.

I figured as much, but the name doesn't convey that very well.
Perhaps something like "native" would be better than "nonshort".

> Personally, I want every decoder to output the most ideal
> format and bitdepth for the audio track. And this is not the
> same for every decoder. So the "non short" flag just tells the
> decoder to output what it likes best.

I agree.  This is how video is handled.  To do this for audio, we'd
first need a generic way of converting between different sample
formats.

-- 
M?ns Rullg?rd
mans at mansr.com