[alsa-devel] Garbage at end of playback: ecasound or alsa broken?

Knut Petersen Knut_Petersen at t-online.de
Sat Jul 20 10:39:58 CEST 2013

Hi everybody!

Summary: A very short period (about 45ms) garbage is played at the end of every playback.

mobo: AOpen i915GMm-hfs
cpu: Pentium-M
ram: 2GB
intel hda, realtek codec
rme digi96/pad
onboard intel hda, realtek alc880

opensuse 12.3
linux kernel 3.10.1, 3.11-rc1
ecasound, git ab6a9c3be5440b05f2c9eb240ee0d42578379f8d

Steps to reproduce the problem:

1: generate test file
Start audacity, generate  a 44.1 khz stereo track,
one second audio, start 400 Hz, end 4000Hz,
start amplitude 0.5, end amplitude 1.0
export to testin.wav as 16bit wav

2: playback test file and record it
Setup soundcards and cabling, execute
"ecasound -t 2 -f:16,2,44100 -a:1 -i testin.wav -o alsahw,0,0  -a:2 -i alsahw,0,0 -o testout.wav"

3:Expected result:
testout.wav should hold a proper recording of testin.wav, padded with silence at the end.

4: my result
1 - starts with about 90 Samples of silence (not nice, how can I avoid that?)
2 - continues with 1 second of properly recorded audio (expected)
3 - continues with about 1982 samples of audio (0,045s) (unexpected, severly broken)
      The garbage audio is part of the original audio, starting at about 26xxHz, ending at about 28xx Hz
4 - continues with silence to the end of the file (expected)

The same problem exists if I record rme96 to rme96, hda to rme96 or hda to hda.
So it´s probably not a problem of the rme96 or hda alsa drivers.

Is this problem known? Can anybody confirm the problem with different hardware?
Should I blame alsa or ecasound? Any ideas?


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