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CaptainBlood
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Joined: 24 Jan 2010
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PostPosted: Sat Jun 02, 2018 10:23 am    Post subject: ffmpeg@gcc-graphite odd behavior... Reply with quote

Ffmpeg audio file start & end trimming works fine ... except that it often replaces a new end near audio chunk by silence.
The very end of the new file is generally fine though.

I switched back from latest ~am64 to stable, cancelled all /etc/portage.package.env specifics but trial for gcc -O1.
It didn't seem to fix properly.

Anyone with the same issue?
Any idea how to fix?
Or maybe an convertfree alternate tool?

Thks 4 ur attention.


Last edited by CaptainBlood on Tue Jun 05, 2018 8:40 am; edited 5 times in total
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CaptainBlood
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Joined: 24 Jan 2010
Posts: 868

PostPosted: Sat Jun 02, 2018 4:48 pm    Post subject: Reply with quote

Old: Had to fallback to media-video/ffmpeg-3.2.6 which didn't punch the file I was working on.
I will return if fallback reveals to be only partial fix.

New: Maybe a frame rate thing...
AFAIK, codecs have default frame rates, so might be worth trying higher frame rates.
But can't find such a parameter. Any idea?

Thks 4 ur attention, interest & support.
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CaptainBlood
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Joined: 24 Jan 2010
Posts: 868

PostPosted: Tue Jun 05, 2018 8:17 am    Post subject: Reply with quote

Real culprit was some among these gcc manually defaulted flags:
Code:
-floop-block -floop-interchange -floop-strip-mine -ftree-loop-distribution -ftree-loop-linear

I initially though these could at worst slow down execution.
Now it reveals to modify (corrupt? ) features, possibly.
I now have too little time to investigate which, but will do in a near future.
I will update from then on.
Any advice?
Thks 4 ur attention, interest & support.

EDIT 1: Hearable differences such as silence holes have been confirmed via media-lib/chromaprint features.
After graphite flags cancellation, ffmpeg doesn't generate auditable silences anymore.
Unrebuilded x64 stable chromaprint keeps showing some differences at the concerned audio chunk, flating the wave though.
EDIT 2: Rebuilded chromaprint too...
EDIT 3: Audacity wave views confirms unflated chunk.
EDIT 4: chromaprint display of latest win ffmeg @git under wine processed file shows same erroneous flatness.
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