Sound volume is very low when playing mkv file

[longkas]

gst-launch-1.0.exe -v playbin uri=file:///g:/me.mkv

Comparing to mp4 files, why sound volume is very low coming out from mkv
files

BR



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[longkas]

I'm not sure if it is because the audio stream in the mkv has 6 channels, I'm
using decodebin to translate streams, maybe I could combine it into 2
channel audio streams, I need some help


BR



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[longkas]

Ok, my research is to use volume element to raise the volume, and use
audioconvert to downmix the 5.1 DTS audio to stereo, I dont know how to find
the current volume though:

gst-launch-1.0 -v filesrc location=g:/gtg.mkv ! decodebin !
audio/x-raw,channels=6 \
     ! audioconvert mix-matrix="<<(float)1.0, (float)0.0, (float)1.0,
(float)1.0, (float)1.0, (float)0.0>, <(float)0.0, (float)1.0, (float)1.0,
(float)1.0, (float)0.0,(float)1.0>>" !   audio/x-raw,channels=2  \
    ! volume volume=10.0  ! autoaudiosink





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[Tim Müller]

On Wed, 2019-05-22 at 07:23 -0500, longkas wrote:

> I'm not sure if it is because the audio stream in the mkv has 6
> channels, I'm using decodebin to translate streams, maybe I could
> combine it into 2channel audio streams, I need some help

What codec/format is the audio stream (gst-discoverer-1.0 -v file.mkv)?

And what decoder is being used in your case? (see output of gst-play-
1.0 -v or gst-launch-1.0 -v)

Is the decoder outputting 2 channels or 6 channels?

It might be that this is caused by e.g. AC-3 audio being downmixed to 2
channels improperly.

Cheers
 -Tim
--
Tim Müller, Centricular Ltd - http://www.centricular.com

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[longkas]

Hello,
Another problem, after I raise the volume, I encode the audio with AAC, but
when I playback there's sometimes glitchy or noisy sound:

#no problem pipeline
gst-launch-1.0 -v filesrc location=d:/file.mp4 ! decodebin ! audioconvert !
audioresample ! audio/x-raw,rate=48000,channels=2 ! volume volume=10.0 !  autoaudiosink

#noisy pipeline
gst-launch-1.0 -v filesrc location=d:/file.mp4 ! decodebin ! audioconvert !
audioresample ! audio/x-raw,rate=48000,channels=2 ! volume volume=10.0 ! voaacenc !
avdec_aac ! audioconvert ! audioresample ! autoaudiosink

By replacing voaacenc to avenc_aac can improve the issue, but it still
happens, what's the problem here,
I tried to add queue, increase  encoder bitrate, no help.  
I tried to using mp3 encoder, even worse, so how does volume=10.0 causes
that？

BR



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