[MPlayer-dev-eng] [PATCH] patch for af_hrtf to relieve noises

[Xidorn Quan]

On Sun, Oct 21, 2012 at 6:44 PM, Xidorn Quan <quanxunzhen at gmail.com> wrote:

> On Sun, Oct 21, 2012 at 4:00 PM, Vladimir Mosgalin <
> mosgalin at vm10124.spb.edu> wrote:
>
>> Hi Xidorn Quan!
>>
>>  On 2012.10.21 at 10:45:19 +0800, Xidorn Quan wrote next:
>>
>> > > On Sat, Oct 20, 2012 at 11:21:32PM +0800, Xidorn Quan wrote:
>> > > > Hi,
>> > > >
>> > > > A simple patch is attached which is intend to relieve noises for
>> > > > af_hrtf by using clamp instead of casting directly.
>> > >
>> > > Not sure if overflows are supposed to be possible, it might just hide
>> > > an issue somewhere else.
>> > >
>> >
>> > Well, I think it is true that it hides an issue somewhere else since
>> > there are still some noises after clamping when remixing stereo. This
>> > patch only relieve some of the noises.
>>
>> Clamp will produce distortion just as well..
>>
>
> Yes, but at least it can significantly alleviate noises at present.
>
>
>> Maybe hrtf filter doesn't use correct (properly downscaled) coefficients
>> or something when downmixing?
>>
>
> I do not know exactly what's wrong inside the filter yet. But as
> I have said above, I will try to solve this problem thoroughly when
> I have time.
>
>
>> It's quite common problem for hrtf filter to cause crackling noise when
>> there is loud sound in original multichannel track. For many tracks it's
>> a must to use something like -af volume=-5,hrtf and for some very loud
>> tracks in action movies sometimes even volume=-10 is required. In
>> neither case original tracks have overflows in any channel, they are
>> produced in hrtf filter itself.
>>
>
> Decreasing the volume can indeed relieve the noise as well. And since
> it could overflow, I think it is a good idea to clamp it.
>
> BTW, the patch using av_clip_* instead has been attached.
>

Applied.