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

[James Almer <jamrial@gmail.com>]

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?

> 
> - 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.
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