iPod mini 2G stutters when playing LAME aps, Clock speed optimisation is the cause Options

[sehested]

iPod nano/mini 2G use clock speed optimisation to increase battery time.
VBR songs with a sudden increase in bitrate may cause the iPod nano/mini 2G to stutter as the clock speed is not increased fast enough to deal with the increased bitrate.

This has so far been observed for songs encoded with LAME --preset standard and is only true when not using the equaliser.

Examples of songs that stutters can be found here:
David Bowie - Five Years
Nine Inch Nails - Right Where it Belongs

For Five Years the clock speed hovers around 24 jumping to 30 when the stuttering begins. Using the equaliser the clock speed hovers around 36 throughout the song and no stuttering occurs.

Further observations:
- this problem is related to the iPod nano/mini 2G but one sample has been found that makes the 4G Color iPod stutter
- problem with iPod mini software 1.3, 1.4, and 1.4.1
- problem with iPod nano software 1.0, and 1.1
- iPod mini 2G do not use optimisation when connected to a computer
- iPod mini 2G do use optimisation, both when using its battery and when connected to a powered dock that is not connected to a computer
- problem go away when using an EQ setting different from flat/off
- only safe EQ setting to use is Bass Reducer / Treble Reducer in order to avoid distortion of songs with a high recording level
- problem do not occur when using iTunes MP3 encoder
- problem do not occur when LAME VBR song do not contain 320 kbps: options --preset standard -B 256
- problem do not always occur at the same spot in the subtle songs listed below
- iPod mini 1G clock speed for Five Years hoovers aroung 31 rising to 33 where it was 24 / 30 for the 2G
- iPod mini optimisation may be turned off (I don't now how to provoke this) and require a reset of the iPod to turn it back on.
- for the 4G color iPod only the sample with NIN - Right Where it Belongs stutters, even with the EQ set to Bass Reducer. Acoustic EQ setting makes the problem go away.

Songs having the problem (obvious):
- Johnny Cash - A Satisfied Mind
- David Bowie - Five Years
- Nine Inch Nails - Right Where it Belongs
- Cake - Nugget @ 26s

Songs having the problem (subtle):
- Eminem - Drug Ballad
- Eminem - Kill You
- U2 - Miracle Drug
- Musica XM - AWS Hope Xm cut

Album songs not having the problem:
- Pink Floyd - Dark Side of the Moon
- Styx - Pieces of Eight
- Guns N' Roses - Illusions I
- Shirley Bassey - Greatest Hits/This is my Life

Edited: Updated list of songs and albums.
Edited: iPod mini 1G do use speed optimisation. My iPod mini 1G was stuck at a clock speed of 80 and required a reset forcing it to use speed optimisation.
Edited: One user with iPod mini 2G was unable to reproduce problem.
Edited: Work around described
Edited: Added NIN
Edited: Added Cake
Edited: Updated for iPod mini software 1.4
Edited: Added Johnny Cash and updated observations
Edited: Added information about 4G color iPod stuttering
Edited: iPod nano stutters as bad as iPod mini 2G
Edited: Updated for iPod mini software 1.4.1 / iPod nano software 1.1

This post has been edited by sehested: Feb 24 2006, 07:40

[Lucas]

my 2G ipod mini skips with 192k cbr songs too.. very randomly also.. so I don't think it's just the bitrate.. some frames might be harder to decode than others even if they're the same size, right? if not, I don't get it.

Where do you check the clock speed?

edited: typo

This post has been edited by Lucas: Apr 24 2005, 00:52

[sehested]

my 2G ipod mini skips with 192k cbr songs too.. very randomly also.. so I don't think it's just the bitrate.. some frames might be harder to decode than others even if they're the same size, right? if not, I don't get it.

Could you please provide a sample of a CBR song that skips?

Where do you check the clock speed?

To view the clock speed of an iPod (Windows version) do the following:
Connect iPod to your computer
Launch Windows Explorer
Change folder settings to show hidden files and folders. Also don't hide file type of known files
Create an empty file named "_show_speed" in iPods iPod_Control\Device folder
Picture of Windows Explorer displaying show speed configuration
Disconnect the iPod
Set Date & Time setting "Time in title" to On


Side Note: Is there a simple way to place pictures in posts, when you don't have your own web server?

This post has been edited by sehested: Apr 24 2005, 09:43