It is commonly said here that if I want to make AM radio-quality stuff at very low bitrates, a good way is to downsample. I downsampled a song to 11025Hz mono and encoded with -q 0, the result is about 18kbps and is at least radio quality. The downsampler I used is from Edinburgh speech tools, named ch_wave. `sox' performs terribly, so I didn't use it. However, I heard some unpleasant sound at relatively high frequencies in the *downsampled WAV file*, but not in the encoded OGG file. So I assume I need some even better downsamplers. Is there any on Linux? P.S. Why not put such downsampling things in the encoder, activated when the quality setting is really low? Or better, save bits by some way cleverer than downsampling? <p><p><p><p><p><p><p><p>__________________________________________ È«³¡ÌؼۣºÊýÂëÏà»ú¡¢ÕÆÉϵçÄÔ¡¢MP3 http://shopping.263.net/category21.htm ÌìÓ®³´¹É,ÌìÉúÎÒÓ®! http://stock19.263.net/download/borntowin.htm <p>--- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
On Sun, 27 Jan 2002, [UNKNOWN] ï¾ûï¾û wrote:> It is commonly said here that if I want to make AM radio-quality > stuff at very low bitrates, a good way is to downsample. > I downsampled a song to 11025Hz mono and encoded with -q 0, > the result is about 18kbps and is at least radio quality. > The downsampler I used is from Edinburgh speech tools, named > ch_wave. `sox' performs terribly, so I didn't use it.Downsampling is a tricky process. One thing to note is that there are several algorithms for doing downsampling in sox, and I think the worst sounding (but the fastest) is used by default. My preferred downsampling command is: ox test.wav -r 11025 test-downsample.wav resample You can also do: ox test.wav -r 11025 test-downsample.wav polyphase Very fast, but very bad results are achieved with: ox test.wav -r 11025 test-downsample.wav rate --- Stan Seibert <p><p>--- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
> It is commonly said here that if I want to make AMradio-quality> stuff at very low bitrates, a good way is todownsample.> I downsampled a song to 11025Hz mono and encodedwith -q 0,> the result is about 18kbps and is at least radioquality.> The downsampler I used is from Edinburgh speechtools, named> ch_wave. `sox' performs terribly, so I didn't useit.> However, I heard some unpleasant sound at relativelyhigh> frequencies in the *downsampled WAV file*, but notin the> encoded OGG file. So I assume I need some evenbetter> downsamplers. Is there any on Linux?As I understand it, when you downsample or upsample with sox, you still need to apply a low pass filter to the output to get rid of the artifacts. I think the oggenc does this by default which is why you don't hear it in your ogg file. I have never seen a good example of what values to use with a low pass filter in sox. Does anyone have any idea of common values to use for down/up sampling? Peter __________________________________________________ Do You Yahoo!? Great stuff seeking new owners in Yahoo! Auctions! http://auctions.yahoo.com --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.