ActiveAE: clamp floats

[FernetMenta]

see title. if ffmpeg does not convert values, the may be out of -1.0 .. 1.0
This is same strategy as SoftAE.

[davilla]

aside from being worried as to where this large error is coming from, ok to inject. I wonder if some of their arm asm code is buggy.

[FernetMenta]

sorry, I was wrong here. this is caused by downmixing to 2.0. will check ffmpeg code if there is a change to have swresample care of this.

[fritsch]

I don't fully understand the weighting, that ffmpeg does, they always scale with 1/sqrt(2) - but 2*sqrt(2) != 2 ... but gets us obviously a boost of the volume :-)

[FernetMenta]

there is a two months old commit in ffmpeg which allows setting max value for rematix:
FFmpeg/FFmpeg@e2b7184

for now I would keep this pr as is because we need clamping anyway when mixing streams for paplayer.
if desired we can only apply this clamping if sink format is float.

[fritsch]

paplayer mixing on song change could be handled separately or better: more carefully. Having that commit backported would save us the whole fabs on all samples.

[FernetMenta]

so you rather have the fabs in ffmpeg than the fabs here? it's not only the fading of streams of paplayer but also gui sounds. you are welcome to provide a better solution :)

[fritsch]

If I see that right, that ffmpeg patch does not clamp, but scale. It keeps the natural distance between the samples, which I like - but and here youre point is valid, we have no guarantee for sounds we produce ourselves and have to clamp those again alone without ffmpeg.

So doing both, should improve sound quality?

[FernetMenta]

convinced. I'll backport it.

[FernetMenta]

updated. now swresample does the clamping for rematrix, we do after having mixed audio

[fritsch]

@FernetMenta: Thanks very much.

jenkins build this please

@davilla: Could you verify on your setup, if it is okay with FLT again?

[fredphoesh]

Hello guys,
Pardon if I should not be writing here, but I was directed to this github conversation from a person on xbmc who said my audio issue was a "known issue". I am not a coder, but am very willing to test builds to see if the audio distortion issue is fixed. I have also uploaded 7 different well known tracks which all display the distortion issue very well. They are here - https://db.tt/uSuCOsi3
Anyhow, I would be glad to help if that would be useful to you. My xbmc thread is here
http://forum.xbmc.org/showthread.php?tid=174202
Cheers guys, Mark.

[davilla]

sounds ok on arm, ok to inject from me.