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BPMs, REX files, Sample rates, PPQ, 1440 as a magic number. Posted by Macintush (the artsits formerly known as Macintorch, aka Ebony Zerascrooj) (from: 207.32.33.94) on August 20, 2002 at 20:03:47: In Reply to: sample rates posted by Ron Cochrane on August 19, 2002 at 05:20:43: Perhaps it's an issue of the BPM. I know that Logic Fun, Cubasis, and other multitrack programs can do odd things to arrangements if there are BPM adjustments. On many such programs, changing the BPM after an audio file is loaded shortens or lengthens the audio file(s) or changes their speed. Other times the timing is corrupted by quantization or grid settings. This is an aside, but 44.1 doesn't cope too well with metric rhythm. 44.1 doesn't divide evenly into most meters at many BPMs. Interestingly, 96 and 48 kHz does a bit better. When you think about PPQ (MIDI pulses per quarter note) and the like, it makes sense that more advanced MIDI timing systems use numbers like 1440 as clock pulses. 1440 is evenly divisible by 1,2,3,4,5,6,8,9,10,12,16,32,60, and 96 to name a few integers. In fact, 1440 is a useful number in all kinds of memory and timing math. This is not so much an issue for you, probably. But if your sequencer is trying to split up 44100 samples per second into corresponding quantities of notes in a musical measure, it could account for a little bit of the timing errors. Another possible issue is if you are confusing mono and stereo files. On a few programs, a stereo file read as a mono file has a difference in speed. Similar errors can happen if a 16bit program reads a 20, 24, or 32 bit file. I have intentionally induced some of these errors via experimentation using SoundHack on the mac. If you are meddling with REX files, I can only imagine how tricky it gets. REX files are designed to have stretchy BPMs and durations and speeds, so watch out if you are mixing REX files and other file formats. Follow Ups: Post a Followup Name: E-Mail: Subject: Comments: : Perhaps it's an issue of the BPM. I know that Logic Fun, Cubasis, and other multitrack programs can do odd things to arrangements if there are BPM adjustments. On many such programs, changing the BPM after an audio file is loaded shortens or lengthens the audio file(s) or changes their speed. Other times the timing is corrupted by quantization or grid settings. : This is an aside, but 44.1 doesn't cope too well with metric rhythm. 44.1 doesn't divide evenly into most meters at many BPMs. Interestingly, 96 and 48 kHz does a bit better. When you think about PPQ (MIDI pulses per quarter note) and the like, it makes sense that more advanced MIDI timing systems use numbers like 1440 as clock pulses. 1440 is evenly divisible by 1,2,3,4,5,6,8,9,10,12,16,32,60, and 96 to name a few integers. : In fact, 1440 is a useful number in all kinds of memory and timing math. : This is not so much an issue for you, probably. But if your sequencer is trying to split up 44100 samples per second into corresponding quantities of notes in a musical measure, it could account for a little bit of the timing errors. : Another possible issue is if you are confusing mono and stereo files. : On a few programs, a stereo file read as a mono file has a difference in speed. : Similar errors can happen if a 16bit program reads a 20, 24, or 32 bit file. : I have intentionally induced some of these errors via experimentation using SoundHack on the mac. : If you are meddling with REX files, I can only imagine how tricky it gets. : REX files are designed to have stretchy BPMs and durations and speeds, so watch out if you are mixing REX files and other file formats. Click here to be notified by email when someone replies to your message [ Follow Ups ] [ Post Followup ] [ Music Software Discussion & Help Page ] [ FAQ ]

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