[FFmpeg-user] Input 5.1 DTS, output 2.0 MP3: Atrocious Quality

Bazza lamia at jeack.com.au
Sat May 16 11:11:19 CEST 2015

On Sat, 16 May 2015 07:52:12 +0000 (UTC), Carl Eugen Hoyos
<cehoyos at ag.or.at> wrote:

>Please test the following:
>$ ffmpeg -i inter.dts -ac 2 out16.wav
>$ ffmpeg -i inter.dts -ac 2 -acodec pcm_s32le out32.wav
>$ ffmpeg -i inter.dts -ac 2 -ab 640k out.ac3
>$ ffmpeg -i inter.dts -ac 2 -ab 320k out.mp2

Carl, I did test some of this stuff. It seemed that attempts to
downmix via -ac 2 would work OK for WAV (pcm_s16le) but anytime
converting to other formats (AC3, or MP3s) generated significant
signal overload. However, the channel mixing DID occur. 
A workaround  was to include -af volume=-10dB.

However, although I'm not the poster with the problem, 
I've just done your suggestions and, for me ...

- MP3 suffers overload
- WAVs are OK
- AC3 suffers overload
- AAC are OK
- MP2 are OK
But I'll let him speak ...

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