Sansa Clip+ rockbox audio volume problem

[transcendent12]

Have a strange issue where I get some sort of volume modulation when playing some tracks. Quite difficult to detect definitively. But on one of my albums, (Deloused in the Comatorium by The Mars Volta). In the main congested chorus parts where all the instruments converge) the volume will dip very noticeably and kind of waver. I do NOT get this with standard firmware.
Looked around the forum and haven't seen any other reports of this.

Any technical explanation for why this may occur? I've looked through the settings for any sort of normalisation or DSP effects and disabled them.

[saratoga]

Do you have the compressor enabled?

[transcendent12]

Compressor is definitely disabled. Format of song is MP3 V0 and i tried two separate rips with same results. I also tried playing from external/internal memory and also a 320kbps CBR mp3. Same results. It's quite distracting; a bit like someone randomly varying the volume of/sweep filtering the vocals mid mix.

Don't really notice it on any of my other music. But i know that it will ignore me knowing that it is possibly there depending on the audio content...

[saratoga]

Could be some kind of hardware problem with the amp or mixer on your player, something wrong with the files or our decoders, etc.  From what you've said though I don't have any specific idea. 

[Miarld]

Same here. On tracks that involve wide frequency range (i.e. death metal) the volume tends to alter. Sansa clip+ 3.9.1, no compressor, no problems on original firmware.

[doomsword]

I'm currently having the same problem, checked all the options in sound settings to be sure that everything is off or to 0 value. Tried also to reset to default settings but the problem is still there. No problem with standard Sandisk 1.02.15 firmware.
I noticed the problem while a was listening to the latest Insomnium album (death metal). The files are 320kbps CB Mp3. Here's some detailed info:

Code: [Select]

Audio
Format                           : MPEG Audio
Format version                   : Version 1
Format profile                   : Layer 3
Mode                             : Joint stereo
Mode extension                   : MS Stereo
Duration                         : 7mn 30s
Bit rate mode                    : Constant
Bit rate                         : 320 Kbps
Channel(s)                       : 2 channels
Sampling rate                    : 44.1 KHz
Compression mode                 : Lossy
Stream size                      : 17.2 MiB (99%)
Writing library                  : LAME3.93 
Encoding settings                : -m j -V 4 -q 0 -lowpass 22.1

The problem seems less annoying with higher (more than 0) treble settings. Checked the tags with Mp3tag and they're ok, cleaned all the not important tags (comment, attached image).
I'm using the latest 3.91 firmware, It's the first Rockbox version I'm using on my Clip+, haven't tried previous Rockbox versions. I don't have any plugins installed and last.fm log is off.
Please let us know if you need further information, here's my audio settings:

Code: [Select]

# .cfg file created by rockbox 3.9.1 - http://www.rockbox.org

volume: -29
balance: 0
bass: 0
treble: 0
channels: stereo
stereo_width: 100
replaygain type: track shuffle
replaygain noclip: off
replaygain preamp: 0
crossfade: off
crossfade fade in delay: 0
crossfade fade out delay: 0
crossfade fade in duration: 2
crossfade fade out duration: 2
crossfade fade out mode: crossfade
crossfeed: off
crossfeed direct gain: 0
crossfeed cross gain: -60
crossfeed hf attenuation: -160
crossfeed hf cutoff: 700
dithering enabled: off
timestretch enabled: off
compressor threshold: 0
compressor makeup gain: off
compressor ratio: 4:1
compressor knee: soft knee
compressor release time: 500

[Miarld]

Same here ))) I too notice it mainly on Insomnium's "Through The Shadows", "Unsung", "Down With The Sun". Also it's noticeable on Amaranthe's "Hunger". Insomnium's track have been listened on 320 and flac. Didn't have any similar problems on the same tracks with Clip V2 (most likely it had the previous version of rockbox).

[doomsword]

I uploaded a 10 sec. sample of one on the song that is the causing the problem on Sansa Clip+: I cutted the original MP3 (in my post above all the original details) and exported as WAV file through Audacity. Listened with 3 different headphones (two Sennheiser and a pair of Koss) the problem is present only with Rockbox 3.9.1: no problem with standard firmware and two different players (Samsung and a cheap Packard Bell player).

http://www.megaupload.com/?d=WS1F5ZLE

Please test with Sound Settings I posted above. Thank you so much in advance guys,

[Miarld]

Now I hear on Hypocrisy's - A Taste of Extreme Divinity. There is no problems with jazz/classical/blues, only death metal.

[doomsword]

Hi Miarld, maybe you can upload somewhere just a sample of the track that is causing the problem so the developers can check and fix the issue in Rockbox. Do you (and maybe ALL the users that read this post!) confirm that there's a problem with the sample I uploaded in the previous post?
Confirming or not that the sample is causing the problem would help to understand if there's a problem with our rockbox installation (or settings maybe) or in the 3.9.1 build. Thank you all in advance,

[keyb_gr]

Using 3.10 on my Clip+, I fail to detect anything unusual with this sample when comparing it to my soundcard's output. Then again, I'm not sure when the patch that disabled output mixer AGC on AMSv2 went in or whether it's in 3.9.1. It's been a while.

BTW, -29 dB? On this sample, that would be my preferred volume for something in between HD580 and HD420SL. With the HD590s, I dialed the volume down to less than -40 dB. (OK, 3.10 should be ~3 dB louder, too.)

Anyway, levels seemed quite reasonable in this one considering the genre, only a handful of clipped samples. Was this encoded from a CD rip or sold as MP3?