oss4 exclusive mode

OSS specific Linux discussion (x86/amd64)

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oss4 exclusive mode

Postby angry_vincent » Fri Apr 15, 2011 4:56 pm

I use oss4 only for mpd playback, so i don't need any vmix enabled. I disabled vmix option totally in osscore.conf. Is it make any sense for better quality? Also, there is an option in osscore.conf excl_policy, does it work , when vmix is disabled or do I need to specify smth? And question about rt-kernel, does it make any sense for oss4?
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Re: oss4 exclusive mode

Postby igorzwx » Fri Apr 15, 2011 5:55 pm

angry_vincent wrote:I use oss4 only for mpd playback, so i don't need any vmix enabled. I disabled vmix option totally in osscore.conf. Is it make any sense for better quality?


It depends on what you play and how you play it, on your soundcard, resamplers, and so on.
You may better enable vmix and make test with "ossplay -R" and special sound files.

Code: Select all
$ man ossplay

    -R     Disable  redirection  to  virtual  mixer  engines   and   sample
              rate/format  conversions.  Should  not be used unless absolutely
              necessary.


You may find some info here:
viewtopic.php?f=3&t=4035
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Re: oss4 exclusive mode

Postby angry_vincent » Fri Apr 15, 2011 6:30 pm

I play only lossless tracks (flac and wavpack), also i have some 24bit/96Khz tracks too. My card is ESI Juli@, pretty decent one, support 24bit/192Khz on hardware level.
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Re: oss4 exclusive mode

Postby cesium » Fri Apr 15, 2011 6:33 pm

Well, I'm no quality expert, but I'm told disabling SRC does improve it slightly (you can also test keeping vmix and setting vmix0-src to OFF in the mixer). In order to disable vmix all you need is to set vmix_disabled in osscore.conf (there's also a mixer switch, but the setting in osscore is more thorough).

excl_policy is something different: It prevents programs from overriding vmix themselves (via O_EXCL flag) and taking control of the soundcard. It has no effect when vmix is disabled.
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Re: oss4 exclusive mode

Postby igorzwx » Fri Apr 15, 2011 8:50 pm

cesium wrote:Well, I'm no quality expert, but I'm told disabling SRC does improve it slightly (you can also test keeping vmix and setting vmix0-src to OFF in the mixer).


This is very misleading.
1. Setting vmix0-src to OFF in the mixer does not always set it "OFF" (a kind of bug in vmix, it does not even tell that it fails to set it "OFF").
2. The default resamplers of OSS4 (Fast, High, High+) are very bad. Any HW resampler of any soundcard (except for ancient ISA chips, perhaps) is much better than the default resamplers of OSS4.
3. Therefore, disabling of the default resamplers of OSS4 produces dramatic improvement in sound quality. This can be proved with mathematical exactitude. Some Linux users, however, are not able to hear the difference, because they use PulseAudio, or because they are deaf to music, or both. In this case, the special test files (e.g. 10Hz + 20kHz) may help to detect sound distortions produced by the default resamplers of OSS4. PulseAudo also produces sound distortions which can be detected with the same test files.
4. OSS4 "Production quality" resampler is much better than HW resamplers of old non-HDA soundcards, e.g. ICH4.
5. The quality of OSS4 "Production quality" resampler is comparable to the quality of HW resamplers of Intel HDA soundcards.

For ordinary users, OSS4 "Production quality" resampler might be sufficient for playing flac and other lossless formats. To enable "Production quality", you have to recompile OSS4 viewtopic.php?f=3&t=3543&start=30#p15711

angry_vincent wrote:I play only lossless tracks (flac and wavpack), also i have some 24bit/96Khz tracks too. My card is ESI Juli@, pretty decent one, support 24bit/192Khz on hardware level.


If you believe that your soundcard has a very good HW resampler inside, or if you want to use another (standalone) resampler (such as the Russian "exact scientific resampler"), it makes sense to set the "exclusive mode". This might be achieved with "ossplay -R".

In a word, Petrov's pcm_pay and his plugin for the Russian ultimate player (deadbeef) allows to set the "exclusive mode" and to use the "exact scientific resampler", or play without resampling.

I tend to believe that the Russian "exact scientific resampler" is better than "Production quality". It is very subjective, of course.
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Re: oss4 exclusive mode

Postby angry_vincent » Fri Apr 15, 2011 9:10 pm

I don't see a reason to have vmix-src, i don't need resampling, it's not a Creative sound card or kind of
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Re: oss4 exclusive mode

Postby igorzwx » Fri Apr 15, 2011 9:42 pm

angry_vincent wrote:I don't see a reason to have vmix-src, i don't need resampling, it's not a Creative sound card or kind of


You may need vmix-src, if you also use Skype or SIP Phone, other players, if you want to play videos in YouTube. Otherwise, you may need to reload OSS to get sound in Skype or other applications. If your soundcard has HW mixer (and it is supported by the OSS driver), you may not need vmix-src, but, if there are bugs in OSS, or apps, you may need to reload OSS time after time.

I am very sceptical of digital sound in general. Imagine that your soundcard is perfect. To play a digital signal, it should transform it into an analog signal. This means interpolation, and interpolation can never be exact, by definition. Regardless of soundcard, you get a kind of "ersatz sound", it is as genuine as "ersatz coffee" made from acorns.
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Re: oss4 exclusive mode

Postby angry_vincent » Sat Apr 16, 2011 3:08 am

mplayer, Skype, youtube works without vmix. The discussion leads to nowhere, it seems. I had a question about real-time , make sense for oss4?
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Re: oss4 exclusive mode

Postby igorzwx » Sat Apr 16, 2011 12:35 pm

angry_vincent wrote:mplayer, Skype, youtube works without vmix. The discussion leads to nowhere, it seems. I had a question about real-time , make sense for oss4?


Yes. vmix was designed to fix certain problems. If you have not such problems, you do not need to fix them.
The same is for RT kernel.
If you do not have problems, there is nothing to discuss.
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Re: oss4 exclusive mode

Postby igorzwx » Thu Sep 15, 2011 12:31 am

audiovox wrote:I disagree with you igor, I have found that adding the perceived fixes can have a positive on the audio quality in at least a studio setting.


What do you mean?

Could you explain what you are going to say in a more exact way?
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Re: oss4 exclusive mode

Postby cesium » Thu Sep 15, 2011 12:18 pm

His email address is listed at http://www.stopforumspam.com/ , so I'm guessing it was a spammer...
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Re: oss4 exclusive mode

Postby igorzwx » Thu Sep 15, 2011 12:39 pm

cesium wrote:His email address is listed at http://www.stopforumspam.com/ , so I'm guessing it was a spammer...


To prove that someone is a spammer, you need a kind of "official definition of spammer".

The real problem is that we do not have rules and rituals, and, therefore, we have a kind of anarchy rather than freedom.

There is an example of rules here:
Forum Etiquette
https://wiki.archlinux.org/index.php/Forum_Etiquette

Etiquette
In Confucianism, the term "li", sometimes translated into English as rituals, customs, rites, etiquette, or morals, refers to any of the secular social functions of daily life, akin to the Western term for culture. Confucius considered education, tea drinking, and music as various elements of li. Li were codified and treated as a comprehensive system of norms, guiding the propriety or politeness which colors everyday life. Confucius himself tried to revive the etiquette of earlier dynasties. http://en.wikipedia.org/wiki/Confucianism#Etiquette


It is very simple: if a person violates the rules, certain rules can be applied.
If you have the rules, you can apply these rules to solve a problem, and you do need to prove that someone is a "spammer", or "terrorist", or else.

For example, if you violate traffic rules, certain rules (laws) might be applied "to the facts" http://www.ajs.org/jc/juries/jc_powers_applylaw.asp
If traffic rules are not defined, there might be chaos, disorder and anarchy rather than freedom.
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