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Topic: Converting 6 channel audio to 2 channel stereo- Help needed (Read 50424 times) previous topic - next topic
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Converting 6 channel audio to 2 channel stereo- Help needed

Hi guys,
This is my first post i this forum.
I have recently got a LG 3D smart Wifi TV for my home. I have many 3D HSBS blue ray rip movies in my hard disk which i would like to play in my tv( MKV, AVI, MP4 format). The TV supports all format and i am able to plug and play all movies from hard disk. But only problem is the audio. The audio for the HD movies which are 2 channel are perfect and i am able to hear the dialogues perfectly. But in those Bluray rips where the audio is 5.1 DTS/Dolby ( 6 channel) the dialogues are barely audible but the background music are perfect, which is spoiling the whole movie experience. I have tried changing the setting in TV but no improvement at all. Everytime i play the movie, the music background score is loud and dialogue is not properly audible.

I tried converting the movies to 2 channel in format factory and play but that also gives the same result of center channel audio of dialogues being suppressed.

Is there anyway i can re-encode this audio 5.1 and downmix it to 2 channel stereo without dialogues getting suppressed retaining the same video quality of Blueray rip and then play it on my TV.? are there any other softwares for it? can someone help me in detailing on how to do it or give me a pointer to any other tutorial sites on how to do it?. Sorry i am a noob in A/V kindly help me

Thanks
Drashkum

PS: I dont know if this is the right subforum to post this question. Moderators kindly move the topic to appropriate forum if it is wrong and oblige

Converting 6 channel audio to 2 channel stereo- Help needed

Reply #1 –
Give eac3to a try and especially its -downStereo option which is what you're looking for.

Converting 6 channel audio to 2 channel stereo- Help needed

Reply #2 –
Quote from: drashkum on
Is there anyway i can re-encode this audio 5.1 and downmix it to 2 channel stereo without dialogues getting suppressed retaining the same video quality of Blueray rip?
Let's assume you have a mkv-file with a H.264 video-stream, 2 DTS audiotracks and it's the 2nd DTS audiotrack you want to downmix to a, let's say, stereo AC3 audio-stream.

You could use eac3to...
Code: [Select]
eac3to.exe "movie.mkv" 3: "soundtrack.ac3" -downDpl -192
...to create a 192kbps Dolby Pro Logic II AC3-file, which you will have to mux manually afterwards.

You could also use FFmpeg...
Code: [Select]
ffmpeg.exe -i "movie.mkv" -map 0:0 -map 0:2 -c:v copy -c:a ac3 -ab 192k -ac 2 -af "aresample=matrix_encoding=dplii" "movie(downmix).mkv"
...to do it all at once; downmix (DPLII), encode to 192kbps AC3, mux video and the newly created AC3-stream (without the 1st DTS audio-stream) in a mkv-container.

Converting 6 channel audio to 2 channel stereo- Help needed

Reply #3 –
In order to avoid suppressed dialogue / loud effects you need to know the dialnorm value present in the source audio-track.
In the case of Dolby audio tracks, the dialnorm is available in the form of -27/-whatever.
In the case of DTS it mostly defaults to -31dbfs meaning no attenuation is required.
eac3to erases the dialnorm tag during extraction, unless you add --keepdialnorm to your command line arguments.
The dialnorm tag is for the audio decoder in order to apply DRC (mostly the film standard preset), avoiding suppressed dialogue / loud effects during playback.
The problem is that the above applies to Dolby formats and not DTS (although it supposedly supports dialnorm).
If you want to apply DRC to a 2 channel track that has been derived from the multichannel DTS source, you need to export it to flac without any volume level changes by eac3to
and then replicate dolby's DRC system in a DAW application.

Converting 6 channel audio to 2 channel stereo- Help needed

Reply #4 –
Simply honoring dialnorm metadata does not apply dynamic range compression. DRC is handled through separate metadata.

Converting 6 channel audio to 2 channel stereo- Help needed

Reply #5 –
Quote
Simply honoring dialnorm metadata does not apply dynamic range compression.

Of course.
Ignoring it will result in over/under compression.

Converting 6 channel audio to 2 channel stereo- Help needed

Reply #6 –
If you have an knowledge  of audio software should be easy enough in reaper - I can do it easily in Nuendo but it's expensive.