FS#8651 - Screeching, High-Pitched Noise after Crossfade
Opened by Humberto Santana (hhannah) - Tuesday, 26 February 2008, 20:10 GMT
Last edited by Andree Buschmann (Buschel) - Sunday, 30 March 2008, 10:17 GMT
THIS IS A DIFFICULT ONE!
First, I must say that I've found this bug VERY difficult to report, because although quite frequent, it is VERY "slippery" (maybe attempted to be described in the past many times (see [*] below) - from what I found in the flyspray & forums) I kind of feel like a ghostbuster here!. I've been "coexisting" with it since I installed Rockbox in November/07. It is related to crossfading, which I use all the time (main reason for coming to Rockbox!). I will do my best to give the relevant information I've found, and also, I kindly request experts' help/ideas on what to check/try in order to find the causes with more accuracy, if that's necessary in addition to the information I present, in order to solve the bug (please notice that this is NOT a support request!).
- iPod video 80GB 5.5G
- rockbox r16422 (but also happened in previous versions, at least from November/07 to this version)
- mp3 format (both in variable and constant bitrates)
Eventually, shortly after crossfading (or right during the crossfading process), playback stops advancing and a screeching, high-pitched, almost hurting, repeating noise begins. I've attached a recording of the problem so that you can actually hear it (sorry about the sound quality, I didn't find a better way than a mic).
Other functions seem to keep on working normally during this noise problem (wps info, menu browsing, etc). To stop the noise, I've used the Prev on the clickwheel, and the current song re-starts ok. If I attempt a forward skip, the noise continues. If I pause, and then resume, the noise continues. If I reboot, when going back to "now playing", it resumes OK but in the previous song to the bug, close to the end of that song.
Now THIS is the main difficulty with this bug, I haven't found a way to reproduce it precisely (I've invested a lot of time in this, but all I've got is what's describe here). I just use crossfading continuously, and sooner or later, the bug appears. In order to give more information about this, I took two actions. 1. I checked the view options in the "debug menu", and 2. I've tried different setting combinations, discarding possible causes.
1. In the debug menus, I've noticed the following:
- In the "View buffering thread" option, the pcm bar/values rise almost to the top and stay there during the noise. In normal operation, it goes down after the crossfading process. Also, the CPU freq is 30Mhz during the problem.
Typical values on this screen during the problem are (values vary slightly from bug to bug):
track count: 6 (has happened with values 0 to 7, so far)
handle count: 21 (has happened also with i.e values of 18)
cpu freq: 30Mhz (always ends with that value when the bug occurs)
boost ratio: begins with 100% when the problem starts, goes down gradually to 0%. Is the THIS IS THE ONLY VALUE ON THIS SCREEN THAT CHANGES DURING THE PROBLEM, THE OTHERS REMAIL STATIC.
- In the CPU Frequency option (debug menu), the values during the bug are: (ALWAYS)
2. Discarded possible causes
Given that crossfading is enabled (different fade-in and fade-out durations, fade-in delay set to 0, fade-out delay set in tests to a value > 0, fade-out mode set to crossfade), I've tried different combinations for the following settings, but since the bug occurs with or without these settings, I guess they can be discarded as possible causes:
- Equalizer enabled or disabled, different specific values.
- All the other "sound settings" were always in their default values.
- Replaygain enabled or disabled, any mode, clipping enabled or disabled, pre-amp any value.
- Any mp3 bitrates (different kbps and/or variable-constant rates in songs involved during crossfading)
- Shuffle enabled or disabled, any mode.
- Repeat enabled or disabled, any mode.
- All the other "playback settings" were always in their default values.
- Any wps loaded (just in case the theme .cfg could have some effect)
[Also in the attachment a typical .cfg]
3. Additional information
Because I can't be 100% sure that the following information relates to the bug, and because this doesn't happen ALL the times the problem occurs, I just put it here in case it gives someone a clue:
After the problem occurs:
- Sometimes after normal playback is restored, crossfade doesn't work anymore. At the end of the song it sort of begins the crossfading process, but the songs are not mixed finally.
- Sometimes the iPod crushes when operating it after the bug restore, the screen is the theme's wps .bmp, the text displayed "Undefined Instruction at 00069DC4 (0) [code's last 3 digits vary]
- Sometimes browsing and normal menu operation becomes very, very slow
Thanks in advance! And if there is something else that I can do to help, please just let me know.
THESE SEEM TO REFLECT THE SAME PROBLEM:
Similar reports (but most probably not the same?):
Sunday, 30 March 2008, 10:17 GMT
Reason for closing: Fixed
Additional comments about closing: Committed with #16889 and #16890.