Downmixing movie sound to two channels

[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

[Eugene]

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".

Maybe use the original number of channels (0) and the TV will do better downmix ?

[Klausi69]

Unfortunately not. It causes stuttering and retarding audio effects.

[Eugene]

Unfortunately not. It causes stuttering and retarding audio effects.

Maybe small audio bitrate ?

[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.

[Eugene]

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.

[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.

[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 

[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.

[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.