[FFmpeg-soc] [PATCH] AMR-WB Decoder

[Marcelo Galvão Póvoa]

2010/9/9 Marcelo Galvão Póvoa <marspeoplester at gmail.com>:
> On 9 September 2010 05:11, Vitor Sessak <vitor1001 at gmail.com> wrote:
>> On 09/09/2010 02:50 AM, Marcelo Galvão Póvoa wrote:
>>>
>>> On 8 September 2010 06:54, Vitor Sessak<vitor1001 at gmail.com>  wrote:
>>>>
>>>> On 09/07/2010 03:21 AM, Marcelo Galvão Póvoa wrote:
>>>>>
>>>>> Hello,
>>>>>
>>>>> On 6 September 2010 10:13, Ronald S. Bultje<rsbultje at gmail.com>
>>>>>  wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On Mon, Sep 6, 2010 at 5:54 AM, Vitor Sessak<vitor1001 at gmail.com>
>>>>>>  wrote:
>>>>>>>
>>>>>>> On 09/06/2010 02:46 AM, Marcelo Galvão Póvoa wrote:
>>>>>>>>
>>>>>>>> Ok, fortunately I've found the bug!
>>>>>>>>
>>>>>>>> It was just a MIN_ISF_SPACING parameter which I extracted from the
>>>>>>>> reference code but was unsure about it's Q level. After some time, I
>>>>>>>> thought I have it figured out but I was wrong. Now I know the answer
>>>>>>>> the hard way...
>>>>>>>>
>>>>>>>> The clipping and the sharp peaks are gone, the waveforms are really
>>>>>>>> close now!
>>>>>>>
>>>>>>> That's great news!
>>>>>>>
>>>>>>>> Also, the stddev against the reference decoder decreased a
>>>>>>>> lot (it was ~884 before):
>>>>>>>> all_men.awb stddev:   51.72 PSNR: 62.05 MAXDIFF: 1089 bytes:
>>>>>>>> 473600/
>>>>>>>> 473600
>>>>>>>
>>>>>>> stddev of 51 looks pretty good to me for this case.
>>>>>>
>>>>>> Maxdiff of 1089 looks like a lot to me, with a low stddev that
>>>>>> suggests that one particular part is off. Can you trace which part is
>>>>>> off and why (phase shift vs. actual bug)?
>>>>>>
>>>>>
>>>>> Sorry, but can you suggest a way of doing it?
>>>>
>>>> Your method of inverting one sample and summing in audacity would work on
>>>> showing where it is happening (some point will have an amplitude of
>>>> 1089).
>>>> To know if is a phase shift or a bug, you will have to compare visually
>>>> both
>>>> waves.
>>>>
>>>
>>> I don't know exactly how to detect a phase shift this way but the
>>> difference waveform I obtained [1] has some peaks at the sibilant
>>> parts I think. Probably just where the high band is louder.
>>>
>>>>> Also, what do MAXDIFF
>>>>> and the "2" at the end of the command line mean?
>>>>
>>>> MAXDIFF is the biggest difference among two samples. The "2" at the end
>>>> of
>>>> the command line says to read two-byte integers (16-bit). If you were
>>>> comparing video pixels, you would use "1". You can also see the source of
>>>> tiny_psnr.c, it is pretty simple.
>>>>
>>>>> This sample have long silence parts and I'm comparing my floating
>>>>> point implementation to the reference 16-bit fixed point. How close
>>>>> you think they should be?
>>>>
>>>> A very small stddev (<  1.00) would assure there is no bug in your
>>>> decoder,
>>>> but the fact that it is large does not means there is one.
>>>>
>>>> I suggest you do the following test:
>>>>
>>>> a) Get a biggish file (>  30 minutes)
>>>> b) Convert it to the a WAV with the sample rate and number of channel the
>>>> AMR encoder takes as input
>>>> c) Encode the file obtained in (b) it with the reference encoder
>>>> d) Decode the file obtained in (c) with the reference decoder
>>>> e) Decode the file obtained in (c) with ffamrwb
>>>> f) Compare the stddev of files obtained in (b) and (d) with that of (b)
>>>> and
>>>> (e). If file decoded with ffamr are as close to the original as that
>>>> decoded
>>>> with the reference decoder, it's good.
>>>>
>>>
>>> Results:
>>> $ ./tests/tiny_psnr ~/ref_pod.wav ~/orig_pod.wav 2
>>> stddev: 2599.69 PSNR: 28.03 MAXDIFF:39592 bytes: 76480640/ 76480660
>>> $ ./tests/tiny_psnr ~/my_pod.wav ~/orig_pod.wav 2
>>> stddev: 2600.02 PSNR: 28.03 MAXDIFF:39653 bytes: 76480640/ 76480660
>>> $ ./tests/tiny_psnr ~/my_pod.wav ~/ref_pod.wav 2
>>
>>
>> Hmm, the files have different sizes. Are you sure you are not comparing
>> files shifted of a few bytes? One parameter of tiny_psnr is a shift between
>> the two files. Does
>>
>> tiny_psnr ~/ref_pod.wav ~/orig_pod.wav 2 10
>>
>> Gives a much worse result? If the shift you are using now (zero) is correct,
>> changing it to anything else should make stddev much bigger. Can you also
>> put the wav files somewhere I can download? If you have a problem of quota,
>> you can use our FTP server as explained in [1].
>>
>
> Now that seems weird:
>
> $ ./tests/tiny_psnr ~/my_pod2.wav ~/orig_pod.wav 2 10
> stddev: 2575.45 PSNR: 28.11 MAXDIFF:46172 bytes: 76480630/ 76480660
>
> $ ./tests/tiny_psnr ~/my_pod2.wav ~/orig_pod.wav 2 -20
> stddev: 2524.06 PSNR: 28.29 MAXDIFF:45328 bytes: 76480640/ 76480640
>
> $ ./tests/tiny_psnr ~/my_pod2.wav ~/orig_pod.wav 2 200
> stddev: 2090.99 PSNR: 29.92 MAXDIFF:46167 bytes: 76480440/ 76480660
>
> I will upload the files later. Probably it will take some time.
>

Ok, I've put them in /MPlayer/incoming/AMR-WB


-- 
Marcelo