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Downmixing movie sound to two channels
Posted: Fri Nov 05, 2010 4:41 pm
by Klausi69
Hello,
when I play movies on my Philips TV screen, I select transcoding profile "Movies primary" with default settings and audio channels quantity = 2. In case of playing movies with 6channel-sound (AC3), the volume is quite poor. I've read that ffmpeg doesn't offer perfect downmixing and lacks of dynamic range compression. Is there a good way to improve sound quality? When I view these movies on VLC, the best menu setting is "Audio Device - 5.1".
Thanks for your support (and for Eugene's brilliant software).
Klausi
Re: Downmixing movie sound to two channels
Posted: Fri Nov 05, 2010 6:00 pm
by Eugene
Hello,
Klausi69 wrote:
when I play movies on my Philips TV screen, I select transcoding profile "Movies primary" with default settings and audio channels quantity = 2. In case of playing movies with 6channel-sound (AC3), the volume is quite poor. I've read that ffmpeg doesn't offer perfect downmixing and lacks of dynamic range compression. Is there a good way to improve sound quality? When I view these movies on VLC, the best menu setting is "Audio Device - 5.1".
Maybe use the original number of channels (0) and the TV will do better
downmix ?
Re: Downmixing movie sound to two channels
Posted: Sat Nov 06, 2010 11:42 am
by Klausi69
Unfortunately not. It causes stuttering and retarding audio effects.
Re: Downmixing movie sound to two channels
Posted: Sat Nov 06, 2010 11:54 am
by Eugene
Klausi69 wrote:Unfortunately not. It causes stuttering and retarding audio effects.
Maybe small audio bitrate ?
Re: Downmixing movie sound to two channels
Posted: Sat Nov 06, 2010 9:03 pm
by Klausi69
My setting of audio bitrate is only 160.000 bit/s. This should be acceptable.
Unfortunately my Philips TV is very unreasonable concerning input signals. This is the reason why I know the merits of your software for months.

Re: Downmixing movie sound to two channels
Posted: Sat Nov 06, 2010 9:23 pm
by Eugene
Klausi69 wrote:My setting of audio bitrate is only 160.000 bit/s. This should be acceptable.
Sound problems due to the small bitrate. You can use any other transcoder, but I would increase the audio bitrate.
Re: Downmixing movie sound to two channels
Posted: Sat Nov 06, 2010 10:52 pm
by Klausi69
You're right. After increasing the bitrate, there isn't any stuttering anymore. But the downmix in my TV is poor. I think I should read the documentations about mencoder. Perhaps there are new possibilites to optimize sound.
Re: Downmixing movie sound to two channels
Posted: Sun Nov 07, 2010 8:23 am
by Eugene
You can also use DirectShow filters, as a basis to take the "Movies - CoreAVC", an example of a
downmix in transcoding profile "Movies - WMF" (used FFDShow Audio Decoder)
Code: Select all
WmsDirectShowSetProperty(sAudioDecoder, IFFDShowBaseT, 2481, 1); // Mixer
WmsDirectShowSetProperty(sAudioDecoder, IFFDShowBaseT, 2482, 1); // stereo
Re: Downmixing movie sound to two channels
Posted: Sun Nov 07, 2010 6:59 pm
by Klausi69
Thanks for your support. Your hint to use DirectShow Filters sounds interesting, but complicated. I think, first I have to learn basics to modify the scripts to get good results.
Re: Downmixing movie sound to two channels
Posted: Fri Nov 12, 2010 8:35 pm
by Klausi69
When I simply try to select Movies-WMF I got error 80040216. I assume that some objects (ffdshow.ax in subfolder "filters"?) are missing. Do you mean that I can change to Movies-CoreAVC without having CoreCodec 2.0, then modifying that script and as a result I get a downmixed sound? Unfortunately I didn't find many information about profile WMF and CoreAVC in this forum. This makes it difficult for me to reconstruct your idea of taking some changes to get the best result.