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slackfriend 05-16-2010 05:53 PM

Slackware64 -current: Self-built Audacity displays garbled waveforms
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Slackware64 -current: Self-built Audacity displays garbled waveforms when running X11 in accelerated mode

Hi everybody,

using the brandnew Slackware 13.1 RC1 (64-bit) [Slackware64 -current], I have built wxGTK-2.8.11 and audacity-1.3.12. For this I used the SlackBuilds from SBo for v2.8.10 and v1.3.7, respectively, with the following modifications:

- both SlackBuilds: editing lines concerning the new source package names and -versions
- wxGTK-2.8.11: removed the "newgtk.patch" from SlackBuild (the content of the patch is already incorporated in the sources) and added '--with-libpng=sys' to the configure-line.

There had been no problems building the packages, both processes run flawlessly.

Audacity starts up and runs with no problems at first glance. But when opening a soundfile and displaying waveforms with some vertical expansion of the waveform-window, there are severe visible distortions of the displayed waveform (of course, NO distortion of sound playback). Because of this, audacity is unusable as a soundfile editor. After some investigations and trial and error it turns out, that the garbled output in the waveform-window seems to be related to the X11 video driver: the distortions disappear when running X11 in NON-ACCELERATED mode. (Video driver: xf86-video-ati-6.13.0-x86_64-1, Video device: ATI Technologies Inc RV710 [Radeon HD 4350]).

Garbling of the waveform image only occurs when X runs in accelerated mode. Changing the accelerated mode from 'EXA' to 'XAA' makes no difference.

Because it is difficult to verbalize, I have attached three screenshots, describing the problem. Downloading the images to the same directory and viewing them with 'Geequie' allows direct comparison.

The problem also appears with wxGTK 2.8.10 and audacity 1.3.7 using the unmodified SlackBuilds from SBo. The problem DOES NOT appear in Slackware 13.0 (32-bit) with wxGTK 2.8.10 and audacity 1.3.7 using the 'fglrx'-driver ( Catalyst 10.3, fglrx 8.712).

Not mentioned above: Running (and building) Audacity requires libsndfile. I built libsndfile 1.0.21, using the SlackBuild from SBo for v1.0.20 (only modified the version number).

A similar (or identical) long standing (since 2009-05-05) problem is mentioned by Alain Perrot ( UMS: Audio curves display corrupted in Audacity with radeon and EXA on RV670, ) for Audacity 1.3.7 on a Kubuntu 9.04 system. In this discussion Dave Airlie pointed out: "This is a UMS bug only, it could happen with KMS, its just extremely unlikely.". I haven' t tested kernel-mode setting with Slackware 13.1 RC1 (64-bit), but will try it soon.

It is to be regretted, not to be able to use the open source highlight Audacity in Slackware 13.1 RC1. :( Perhaps someone has any ideas or knows a solution. :)

Nevertheless, and last but not least big thanks to Pat Volkerding and the crew to push forward Slackware development until now.


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disturbed1 05-17-2010 04:38 PM

Have you read this thread?

Bug report to Xorg with a possible working patch. Wx has a bug report, refered to Red Hat. Acknowledged it is ATI driver/hardware related.

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