Time Compression -Sound Forge - PC - MAGIX Community Forums Archive

Subject:Time Compression Posted by: nlavon Date:5/31/2002 1:54:43 PM I needed to add about 35 seconds to a 25-minute radio program and used Sound Forge 6.0a's Time Compression to do it. It came out to about a 3 percent increase on the fader. There is some music at both ends, about thirty seconds each, and the rest, talk. I saved the .wave file as a 128 Mhz mp3 file, slapped it on a CD and brought it to work. I thought the sound was a little wobbly in places, and I thought it should have sounded a little better. What is a good setting for mode when trying to stretch a piece like this? Thanks for any help.
Subject:RE: Time Compression Reply by: Chienworks Date:5/31/2002 2:04:35 PM I'm assuming you were using Process / Time Stretch. The modes are optimized for different kinds of program material. What works well for speech might not work well for music. You may want to select different portions of the file separately and stretch them with different modes. Another alternative for minor amounts of stretching is to use Effects / Pitch / Bend. Since you only needed to add 3% to the length, this option would simply slow the playback down instead of the complex processing that time stretch involves. It would drop the pitch approximately half a semitone, but that probably wouldn't bother anyone, especially those who haven't heard the original material. One other question, why save as mp3? A CD will hold 74 minutes of 44KHz 16 bit stereo .wav. I would think you would want to preserve the quality as much as possible and it wouldn't seem like your space limitations would require compression.
Subject:RE: Time Compression Reply by: nlavon Date:5/31/2002 4:07:43 PM Unfortunately, where I work uses a proprietary digital editing system called Dalet. I believe it's a French company that has made such systems for broadcast news organizations (I work for Voice of America in Washington). The only file that Dalet seems to accept without problems are .mp3's. Sometimes they take .wav files, but not all the time. Perhaps next time I can try it as a .wav for better quality and see if that works in Dalet. I'll try and see if other modes--speech, etc--work any better. The pitch bend may be another way. We used to have tape machines that ran at 7.45, 7.40. 7.33 ips instead of the normal 7.5 and I'm sure there were differences in tone but not noticeable, at least not very to an untrained ear. But one of the reasons I bought Sound Forge was to get that time compression capability. I'll try some other settings and see how they work as well as the pitch/bend. Thanks for the tip and this is a great forum.
Subject:RE: Time Compression Reply by: joelogan Date:6/1/2002 10:50:35 AM Here’s another idea… Since a portion of your program is talk, add small spaces between sentences. A .150 seconds here and there will really ad up. NOTE: in Windows, CONTROL + Y repeats that last command. I’ve used the time stretch/compress feature quite often, and I’ve never had a whole lotta luck when stretching (or lengthening) the audio. Even compression is only best when used under 8-10% depending on content. Best of luck and let us know how it all works out! Joe

Subject:Time Compression

Posted by: nlavon

Date:5/31/2002 1:54:43 PM

I needed to add about 35 seconds to a 25-minute radio program and used Sound Forge 6.0a's Time Compression to do it. It came out to about a 3 percent increase on the fader.

There is some music at both ends, about thirty seconds each, and the rest, talk. I saved the .wave file as a 128 Mhz mp3 file, slapped it on a CD and brought it to work. I thought the sound was a little wobbly in places, and I thought it should have sounded a little better.

What is a good setting for mode when trying to stretch a piece like this?

Thanks for any help.

Subject:RE: Time Compression

Reply by: Chienworks

Date:5/31/2002 2:04:35 PM

I'm assuming you were using Process / Time Stretch. The modes are optimized for different kinds of program material. What works well for speech might not work well for music. You may want to select different portions of the file separately and stretch them with different modes.

Another alternative for minor amounts of stretching is to use Effects / Pitch / Bend. Since you only needed to add 3% to the length, this option would simply slow the playback down instead of the complex processing that time stretch involves. It would drop the pitch approximately half a semitone, but that probably wouldn't bother anyone, especially those who haven't heard the original material.

One other question, why save as mp3? A CD will hold 74 minutes of 44KHz 16 bit stereo .wav. I would think you would want to preserve the quality as much as possible and it wouldn't seem like your space limitations would require compression.

Subject:RE: Time Compression

Reply by: nlavon

Date:5/31/2002 4:07:43 PM

Unfortunately, where I work uses a proprietary digital editing system called Dalet. I believe it's a French company that has made such systems for broadcast news organizations (I work for Voice of America in Washington). The only file that Dalet seems to accept without problems are .mp3's. Sometimes they take .wav files, but not all the time. Perhaps next time I can try it as a .wav for better quality and see if that works in Dalet.

I'll try and see if other modes--speech, etc--work any better. The pitch bend may be another way. We used to have tape machines that ran at 7.45, 7.40. 7.33 ips instead of the normal 7.5 and I'm sure there were differences in tone but not noticeable, at least not very to an untrained ear. But one of the reasons I bought Sound Forge was to get that time compression capability. I'll try some other settings and see how they work as well as the pitch/bend.

Thanks for the tip and this is a great forum.

Subject:RE: Time Compression

Reply by: joelogan

Date:6/1/2002 10:50:35 AM

Here’s another idea…

Since a portion of your program is talk, add small spaces between sentences. A .150 seconds here and there will really ad up. NOTE: in Windows, CONTROL + Y repeats that last command.

I’ve used the time stretch/compress feature quite often, and I’ve never had a whole lotta luck when stretching (or lengthening) the audio. Even compression is only best when used under 8-10% depending on content.

Best of luck and let us know how it all works out!

Joe