[FFmpeg-cvslog] r18860 - in trunk/libavcodec: ac3dec.c ac3dec_data.c ac3dec_data.h eac3dec.c

Justin Ruggles justin.ruggles
Sat May 23 04:38:41 CEST 2009


Michael Niedermayer wrote:
> On Wed, May 20, 2009 at 09:21:11PM -0400, Justin Ruggles wrote:
>> Michael Niedermayer wrote:
>>> On Tue, May 19, 2009 at 10:13:34PM -0400, Justin Ruggles wrote:
>>>> Michael Niedermayer wrote:
>>>>> On Tue, May 19, 2009 at 06:23:38PM -0400, Justin Ruggles wrote:
>>>>>> Michael Niedermayer wrote:
>>>>>>> On Sun, May 17, 2009 at 08:53:27AM +0200, jbr wrote:
>>>>>>>> Author: jbr
>>>>>>>> Date: Sun May 17 08:53:24 2009
>>>>>>>> New Revision: 18860
>>>>>>>>
>>>>>>>> Log:
>>>>>>>> eac3dec: use 16-bit pre-mantissas instead of 24-bit in AHT decoding. it is
>>>>>>>> simpler and also fixes a bug in GAQ dequantization.
>>>>>>> are you sure 16bit precission is enough for that?
>>>>>>> what effect does this compared to double precission floats have on the
>>>>>>> PSNR ?
>>>>>> stddev:    7.95 PSNR: 78.30 bytes:  3999744/  3999744
>>>>> and what is that?
>>>>>
>>>>> we have raw -> encoder -> ac3 -> double fp decoder -> raw2
>>>>>                               -> 16bit     decoder -> raw3
>>>>>
>>>>> PSNR of raw2 - raw vs. PSNR raw3 - raw is what we care about.
>>>>> That would make 2 PSNR scores though, a before and a after
>>>>>
>>>>> the second part we care about is the difference to a reference decoder
>>>>> that should mention which reference decoder is used though
>>>> I can't compare to raw in this case because I don't have access to a
>>>> professional E-AC-3 encoder which uses the AHT quantization.  But I can
>>>> compare to decoded output from Nero's E-AC-3 decoder.
>>>>
>>>> nero vs. ffac3 svn
>>>> stddev:  131.16 PSNR: 53.96 bytes:  3998716/  3999744
>>> why does the output differ so much to begin with?
>> That I'm really not sure of.  I don't have access to the Nero decoder
>> other than begging madshi to decode samples for me like I did in this case.
> 
> isnt there some official reference decoder like with ISO/ITU standards?

Dolby Media Decoder. List price: $1900






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