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View Full Version : Gapless WAV/FLAC playback



thomyk
2006-02-21, 15:41
By looking around through this board I came to the conclusion that SB should be able to playback WAV and FLAC files gaplessly. But still I am not able to reproduce this.

My system:
Pentium 2,4GHz with Slimserver 6.2.1 running
SB3 connected directly (via ethernet crossover cable) to PC

When I started playing back my audio files (all FLAC 1.1.2) I realized that there is a gap (although a very small one) when transitioning from one track to another. Strangely enough playback of the same files with SoftSqueeze 2.3 does not show this behaviour.

So I started to do some testing on this feature but results were not very satisfactory. With Audacity I created two WAV files of exactly 30 seconds with a 1kHz test tone. I also converted those files to FLAC using FLAC version 1.1.2 (tried 1.1.1 as well, but test results did not change).

I can play back those files gaplessly in Winamp and foobar2000. As mentioned already playback with SoftSqueeze 2.3 is gapless as well. However when I start playing back the files on my new SB3 there is a small click between the tracks.

Did someone see the same behaviour or can someone verify it? Am I doing something wrong here? When playing ripped CD's the gap is sometimes hard to notice but it is definetly there.

I also played around with different Slimserver/SB firmware versions:
- Slimserver 6.1.1 with firmware 15
- Slimserver 6.2.2 nightly build 06/02/20 with firmware 33

The gap when playing back FLAC resp. WAV was not affected and still there. Besides I have some reproducible strange noice (clicking) when playing back the sine tone with firmware 33.

radish
2006-02-21, 18:48
Are you really hearing a gap or a click? They are different things. I get perfect gapless playback on all my tracks, a mixture of flac and vorbis - when both are transcoded and streamed as wav. If I stream as flac and decode on the player I sometimes get a problem where the last 0.5 secs or so is skipped. This isn't a gap - there's no silence - but a click would be audible in many cases. There's a bug report already raised for this issue but disabling native flac should fix it.

Another thing to check is that crossfade and player sync are both disabled.

EnochLight
2006-02-21, 21:33
When I was using 6.2.1 and 6.2.2 it worked fine for me. Now that I am using the 6.5 beta it works fine still.

I have my library in FLAC and decode on my Squeezebox 3 natively in FLAC; crossfade is off when I want to do this.

thomyk
2006-02-22, 15:36
Today as was able to do some more testing. Finally I suceeded in playing back wav files without any gaps:

1. First thing I found out was that SlimServer is by default configured so that wav files are transcoded by the server to FLAC format.

2. By disabling transcoding of WAV to FLAC I could play back my test WAV files without any gap. So far so good. So gapless WAV playback is fine!

3. However when I play back native FLAC files (or WAV files that are transcoded by the server to FLAC format) I hear some noise at the transition between the tracks.

4. To find out how this "noise" looks like in the waveform I feeded the line-out of my SB3 to the line-in of my PC and recorded the transition. Then I looked at the waveform using Audacity. What you can see is that there is no real gap (no silence) at the track change. However it seems as if there are some samples missing!

Are you refering to the following bug:
http://bugs.slimdevices.com/show_bug.cgi?id=1434
It seems to be a similiar problem if not the same. Although I do not see that 0.5 seconds are missing but I guess this is just a rough number.

So for you FLAC playback is working fine. Might this depend on the FLAC version you are using? Which FLAC version are you actually using?

kdf
2006-02-22, 16:21
Quoting thomyk <thomyk.23nk8z1140648301 (AT) no-mx (DOT) forums.slimdevices.com>:

> However it seems
> as if there are some samples missing!

or, that the transition point inverts the waveform, or the new track
starts with a negative swing when the previous song had just ended
with a negative swing.

-kdf

radish
2006-02-22, 17:07
What you can see is that there is no real gap (no silence) at the track change. However it seems as if there are some samples missing!

Exactly.



Are you refering to the following bug:
http://bugs.slimdevices.com/show_bug.cgi?id=1434
It seems to be a similiar problem if not the same. Although I do not see that 0.5 seconds are missing but I guess this is just a rough number.

Yes, that's it (I raised it a looooong time ago). The 0.5s is just an estimate, it's certainly longer than a few samples in many cases (in fact, using a sine wave as you do makes it impossible for you to tell how many samples are actually missing). Thinking about it, seeing as it usually sounds to me like around half a beat at 130bpm, I'd guesstimate 0.25s is closer.



So for you FLAC playback is working fine.
No it's not. I can only use FLAC if I transcode to WAV, just like you. Some people have reported specifically not seeing this problem, but there are enough reports of it to convince me it's a real bug. It must just not manifest itself in some unknown circumstances.


@kdf - I know the audacity screenshot isn't definitive evidence, but there are samples missing, trust me :) The bug report has audio samples clearly demonstrating the problem.

Wombat
2006-03-16, 13:29
I also like to have this bug fixed. It is most annoying in silent parts of music where the resulting trip overs become even annoying.
I hate using wav decoding due to its inability to fast forward or do i miss a setting?

Edit: I can upload a sample that is ~2MB in size for people to play. It should be very easy to hear the problem and iīd like to get feedback of people donīt have this problem afterwards.
Is there any place i can upload it? I donīt want to register on such free webspace pages.

radish
2006-03-16, 17:48
There are already examples on the bug report, but if you want to add your own, do it there.