Re: [FFmpeg-devel] [PATCH] avcodec/aacdec: don't force HE-AACv2 profile if no PS info is present

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

James Almer:
> On 7/22/2022 11:23 AM, Andreas Rheinhardt wrote:
>> James Almer:
>>> On 7/18/2022 10:57 AM, Andreas Rheinhardt wrote:
>>>> James Almer:
>>>>> On 7/14/2022 9:10 AM, Andreas Rheinhardt wrote:
>>>>>> James Almer:
>>>>>>> Should fix ticket #3361
>>>>>>>
>>>>>>> Signed-off-by: James Almer <jamrial@gmail.com>
>>>>>>> ---
>>>>>>> This also needs an update to some fate ref samples i'll upload
>>>>>>> before
>>>>>>> pushing
>>>>>>> (fate-aac-al_sbr_ps_04_ur and fate-aac-al_sbr_ps_06_ur which are now
>>>>>>> decoded
>>>>>>> properly as he_aac mono, so the .s16 files need to be replaced).
>>>>>>>
>>>>>>
>>>>>> We have both a fixed-point AAC as well as a floating point AAC
>>>>>> decoder.
>>>>>> Is there actually a test that tests that the output they produce is
>>>>>> reasonably close? If not, could we make the test so that the same
>>>>>> file
>>>>>> is decoded once with the fixed-point and once with the floating-point
>>>>>> decoder and then compared?
>>>>>
>>>>> That wouldn't help much, i think. Almost all changes to *_template.c
>>>>> files are going to affect both decoders, so a breakage would not be
>>>>> detected if you compare their output with each other as they would
>>>>> both
>>>>> exhibit it.
>>>>>
>>>>
>>>> I actually thought that the aac_fixed tests used checksums instead of
>>>> ref files; then changes and breakages would be visible by changes to
>>>> these files. Apparently I was wrong about that and the ref files are
>>>> used for both aac and aac_fixed. But a test like the one outlined above
>>>> would nevertheless obviate the need for a new ref file.
>>>
>>> Judging by
>>> https://git.videolan.org/?p=ffmpeg.git;a=blob;f=tests/fate/aac.mak;h=1743428f544fad8946dba11dd4ecec0630eb70a6;hb=HEAD#l117
>>>
>>> it seems at least for these samples the fixed decoder does not generate
>>> a decoded stream comparable to the float one, so I'll just upload a new
>>> raw pcm file.
>>
>> When I decode both of these streams with git master, the left channel is
>> pretty much identical, yet the right channel of the fixed-point decoder
>> is silent and the right channel of the floating point decoder is not.
>> With this patch applied, the result are two mono streams that are pretty
>> much identical: The test sample created by the floating-point decoder
>> works with the fixed-point decoder test (if one uncomments and modifies
>> the latter). So the issue with aac-al_sbr_ps_06_ur is not a reason to
>> upload new samples.
> 
> Ok, can you suggest how to add a test that decodes with the fixed point
> decoder then compares that with the output of the float decoder? Is
> there a helper in fate.sh already for this?
> 

There is currently no helper in fate-run.sh for this.

>>
>> - Andreas
>>
>> PS: libfdk-aac produces a file that looks pretty much like the floating
>> point decoder from git master. Are you sure your patch is correct?
> 
> Yes, they duplicate the single channel in the stream and output it as
> stereo, something that should be done by a filter if that's what the
> user wants. Decoding a mono sample should generate a mono stream.

Not really. The channels are different.

- Andreas
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