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| Unofficial VirtualDub Support Forums > Testing / Bug Reports > Audio Conversion And Rate Selection |
| Posted by: yusuf Feb 21 2005, 07:18 PM |
| Hi, I have few old captured files which I want to encode. I only want to use one audio channel from these file (left channel has junk audio). Hence, I select 'Right' option from Audio->Conversion dialog box. This reduces sample rate to ACM by half. This is correctly shown by status bar in Conversion dialog. However, VirtualDub still selects Audio Compressor format with full sample rate by default Although I can obveride it with selecting 'Show All Format' and then selecting right sample rate which is half. It would be great if virtualdub handles this correctly, Yusuf |
| Posted by: Belial Feb 21 2005, 07:22 PM |
| If you only need one channel,then just select right or left.Samplerate should stay the same.Although you might wanna use mono,if you use just one side. |
| Posted by: stephanV Feb 21 2005, 08:38 PM |
| sampling rate has nothing to do with the amount of channels. |
| Posted by: yusuf Feb 22 2005, 05:29 AM |
| I mean data rate |
| Posted by: phaeron Feb 22 2005, 07:37 AM |
| Raw PCM bitrate and compressed audio bitrate are different. Audio channels in PCM are independent, so cutting one channel out of a 176KB/sec CD audio stream drops the output rate to 88KB/sec with no change to the remaining channel's data. Reducing a 64Kbps stereo or joint-stereo MP3 stream to 32Kbps mono is likely to be unexpectedly traumatic to the audio, however. It is best that you choose the target bitrate you want to use for compression. |
| Posted by: yusuf Feb 22 2005, 09:27 AM |
| I think that is not correct. When you are feeding ACM with only one channel data, the default format should be one with half datarate and not full datarate for both channel. |
| Posted by: i4004 Feb 22 2005, 12:20 PM |
| and it is. if you feed mono signal to vdub, and on acm dialog "show all formats" is unchecked, only 'compatible' compression schemes are shown. data rate? mp3 codec lets you select what datarate (bitrate) you want. half data rate of what? what if i used 320kbit/s for stereo? does that suggest only 160kbit/s should be used (or made 'default') for mono? for sure not. as seen in this image; http://bbsrv.imp.leidenuniv.nl/~i4004/0/acm/mp3.png source was 44khz mono. same result should be obtained if you picked only one channel form 44khz stereo signal via 'conversion' . vdub handles this correctly. but 'advanced filtering' option is another story. try resampling to 32khz there, and acm dialog box is not aware of it. |