[FFmpeg-devel] [PATCH] remove out-dated ADPCM frame_size handling in libavformat

[Justin Ruggles]

Michael Niedermayer wrote:

> On Wed, Sep 08, 2010 at 06:49:36PM -0400, Justin Ruggles wrote:
>> Justin Ruggles wrote:
>>
>>> Michael Niedermayer wrote:
>>>
>>>> On Mon, Sep 06, 2010 at 08:11:38AM -0400, Justin Ruggles wrote:
>>>> [...]
>>>>> Index: tests/ref/acodec/g726
>>>>> ===================================================================
>>>>> --- tests/ref/acodec/g726	(revision 25042)
>>>>> +++ tests/ref/acodec/g726	(working copy)
>>>>> @@ -1,4 +1,4 @@
>>>>> -5d8cce28f83dd33c3c7eaf43a5db5294 *./tests/data/acodec/g726.wav
>>>>> -24082 ./tests/data/acodec/g726.wav
>>>>> -4f1ba1af75dee64625a1c852e6cd01d3 *./tests/data/g726.acodec.out.wav
>>>>> -stddev: 8504.69 PSNR: 17.74 MAXDIFF:31645 bytes:    96104/  1058400
>>>>> +fd090ddf05cc3401cc75c4a5ace1d05a *./tests/data/acodec/g726.wav
>>>>> +24052 ./tests/data/acodec/g726.wav
>>>>> +74abea06027375111eeac1b2f8c7d3af *./tests/data/g726.acodec.out.wav
>>>>> +stddev: 8554.55 PSNR: 17.69 MAXDIFF:29353 bytes:    95984/  1058400
>>>> the number of samples encoded seems to be changing and not equal to
>>>> the input
>>> When the frame size in the encoder makes frames end on a byte boundary
>>> without any padding, the output is always identical.  Since codes are
>>> between 2 and 5 bits long, how would the decoder distinguish between
>>> padding to a byte boundary and another valid code?  I'll double-check,
>>> but it seems that the decoder currently treats padding as additional
>>> samples.
>> I've confirmed that this is the cause of the difference.  The parameters
>> used by the regression test give a 4-bit code size.  When the frame size
>> is odd, that leads to 1 extra sample being decoded by the decoder
>> because of padding.  In the current version, because of resampling from
>> 44100 Hz to 8000 Hz, the frame size actually varies from frame-to-frame.
>>
>> Current:
>> source samples             = 264600
>> resampled samples          =  47991
>> number of odd-sized frames =     61
>> decoded samples            =  48052
>> decoded data bytes         =  96104
>>
>> Patched:
>> source samples             = 264600
>> resampled samples          =  47991
>> number of odd-sized frames =      1 (the last frame)
>> decoded samples            =  47992
>> decoded data bytes         =  95984
>>
>> So choosing a frame size that forces the encoder to only use padding for
>> the last frame (which this patch does) seems to be the appropriate thing
>> to do.
> 
> the patch is ok then


patch applied.

Thanks,
Justin