@mp3geek wrote:
I found my wife’s Chromatic tuner again and you guys sparked my interest so I made a few new test files using Audacity and tested them. The results are shown below.
- 440 Hz sine wave at 44100 sample rate encoded with LAME MP3 - 20 cents slow
- 880 Hz sine wave at 44100 sample rate encoded with LAME MP3 - 20 cents slow
- 440 Hz sine wave at 48000 sample rate encoded with LAME MP3 - dead on
- 440 Hz sine wave at 22050 sample rate encoded with OGG - dead on
- 440 Hz sine wave at 96000 sample rate encoded with OGG - dead on
There seems to be a pattern here. Does anyone want to comment.
Note that the real time clock is about 5 minutes slow - but I set it about a month ago.
p.s. I can hear a clear difference in pitch between these files.
http://forums.sandisk.com/sansa/board/message?board.id=sansafuse&message.id=17849#M17849
@donp wrote:
So what level of precision does “consumer electronics” have?
I made 1000 Hz and 1002 Hz wave files in cool edit, converted to flac and ogg/vorbis for the players, and burned to 2 CD’s. Playing 2 sources at the sime time will give a beat frequency equal to the difference in the tones’ frequencies (as anyone who’s tuned 2 instruments against each other knows). The 1002 hz file was a sanity check to make sure I could hear the beat when 2 sources are known to be off… worked in all cases.
Playing Cool edit against foobar on the same PC, flac, wav, or ogg, no beat (everything consistantly in tune)
CD player vs DVD player (both fairly cheap consumer models, different brands and about 20 years apart in age) - roughly 30 seconds per beat (1/30 hz), for an difference of 1 part in 30,000 or 0.003%
CD player or Cool Edit vs Sansa E200 (rockbox playing flac)- beat of ~1/3 Hz, error 1 part in 3000, or 0.03%.
Cool Edit vs Neuros player (playing ogg file) - Also about 1/3 Hz, so 0.03%
Cool Edit vs Clip (playing flac) - beat of 7 Hz, error about 1 part in 140 or 0.7% I checked this one by generating a new wave of 1007 Hz, which was in tune with the Clip playing the “1000 Hz” file.
So the Clip’s pitch error (and presumably play speed error) is over 20x worse than my other portables, and 200x worse than the difference between my CD player and DVD player.
So the typical standard for consumer electronics (including an older Sansa model) really is a lot better than the current lot.
http://forums.sandisk.com/sansa/board/message?board.id=sansafuse&message.id=17849#M17849
From the test results posted so far, it looks like 44.1kHz files are the ones being played back too slow. DonP’s measurement indicated a ~0.7% slowdown. MP3Geek’s measurement (probably cruder than DonP’s due to his methodology) indicated a ~1.15% slowdown (~20 cents).
@My initial suspicion was the same as yours, that 48kHz files were being played back @ 44.1kHz, thus resulting in slowdown. However, if that were the case, the slowdown would be 8.125%, which is far larger than the amount of slowdown indicated by the test results. This suspicion is also defeated by the fact that 48kHz files apparently play back @ normal speed, the problem only occurs when 44.1kHz files are played back (I’m still awaiting more solid confirmation of this though, we’ll know when we see more people post their test results).
The fact that MP3Geek’s Fuze can play some files back at the correct speed indicates that the internal clock mechanism is probably ok, so I think that this problem can probably be corrected via firmware (don’t know for sure though, since I don’t know the device’s internals).
DonP, the sample rate of your test file was 44.1kHz, right?
Message Edited by maxplanck on 02-16-2009 01:46 PM