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  • ALSA: Audio Compression Offloading, Power Savings

    Phoronix: ALSA: Audio Compression Offloading, Power Savings

    Besides lots of graphics talks at the GStreamer 2012 Conference, the Advanced Linux Sound Architecture (ALSA) was talked about with a status report and mentions of some features soon to be landing in future Linux kernel releases...

    http://www.phoronix.com/vr.php?view=MTE3MTQ

  • #2
    Does?

    Does PulseAudio do bit-perfect playback?
    How do I do I set it up to do so?

    Does PulseAudio support THX, Dolby, DTS, SRS, DLNA, surround, virtual surround, etc and all those fancy logos on audio equipment which I have no idea what they mean?

    Does PulseAudio support playing music at different volume on different speakers, and different songs (output streams) to different speakers in different rooms like Sonos multi-room music system?

    Comment


    • #3
      Originally posted by uid313 View Post
      Does PulseAudio do bit-perfect playback?
      How do I do I set it up to do so?

      Does PulseAudio support THX, Dolby, DTS, SRS, DLNA, surround, virtual surround, etc and all those fancy logos on audio equipment which I have no idea what they mean?

      Does PulseAudio support playing music at different volume on different speakers, and different songs (output streams) to different speakers in different rooms like Sonos multi-room music system?
      Who are you talking to?

      Comment


      • #4
        Originally posted by uid313 View Post
        Does PulseAudio do bit-perfect playback?
        How do I do I set it up to do so?

        Does PulseAudio support THX, Dolby, DTS, SRS, DLNA, surround, virtual surround, etc and all those fancy logos on audio equipment which I have no idea what they mean?

        Does PulseAudio support playing music at different volume on different speakers, and different songs (output streams) to different speakers in different rooms like Sonos multi-room music system?
        those are good questions but im not really sure, we need an audio guru

        Comment


        • #5
          Originally posted by bluestealth View Post
          Who are you talking to?
          Nobody in particular.
          I was just asking the questions plain out so anyone who knows can feel free to answer.

          Comment


          • #6
            Originally posted by uid313 View Post
            Does PulseAudio do bit-perfect playback?
            How do I do I set it up to do so?

            Does PulseAudio support THX, Dolby, DTS, SRS, DLNA, surround, virtual surround, etc and all those fancy logos on audio equipment which I have no idea what they mean?

            Does PulseAudio support playing music at different volume on different speakers, and different songs (output streams) to different speakers in different rooms like Sonos multi-room music system?
            As for half of those logos you mentioned, they're either just company names or aren't directly relevant to your sound card. ALSA does support surround sound, but my #1 gripe about ALSA is it's a royal pain in the ass to get surround sound and channel redicting working properly. No matter what guide I follow, something goes wrong. They're not that hard to follow, they just don't work. This is mostly because the way you configure .asoundrc files gets outdated and nobody updates their tutorials. If you want a quick easy way to mux multiple channels, go with PA, it does a pretty good job at that IMO and is the only compelling reason to use PA over ALSA. Even if setting up surround sound in ALSA worked as advertised, PA's CLI methods for setting up surround sound are still easier.

            I'm currently an ALSA user and pretty much always have been. I do have surround sound but I rarely ever need it in linux so I don't care so much that it doesn't work for me.

            Ranting aside, playing music at different volumes on different speakers is generally achieved by a sound server like PA, but you could also just run 2 instances of a program and tell each to redirect the sound to w/e speakers you want it to play on. Pretty much the point of ALSA is to just get your hardware functioning. You use a sound server to do the fancy stuff.

            Comment


            • #7
              Originally posted by uid313 View Post
              Does PulseAudio do bit-perfect playback?
              How do I do I set it up to do so?

              Does PulseAudio support THX

              THX is a brand.
              Originally posted by uid313 View Post
              Dolby
              also a brand

              Originally posted by uid313 View Post
              DTS
              AFAIK: Yes, you can do DTS passthrough.

              Originally posted by uid313 View Post
              SRS
              You mean the audio processing stuff that makes your music sound terrible? No, but it is often done on the stereo receiver anyway.

              Originally posted by uid313 View Post
              DLNA
              There is no reason a sound server would even consider supporting DLNA. If you want to access a DLNA server use XBMC.

              Originally posted by uid313 View Post
              surround
              Yes, PA can do more than 2 channels.

              Originally posted by uid313 View Post
              virtual surround
              Yes, it can also upmix to more than 2 channels.

              Originally posted by uid313 View Post
              etc and all those fancy logos on audio equipment which I have no idea what they mean?
              If you don't know what they are why do you care. Also, most of those are only needed by the thing that has the stickers on them.

              Originally posted by uid313 View Post
              Does PulseAudio support playing music at different volume on different speakers, and different songs (output streams) to different speakers in different rooms like Sonos multi-room music system?
              Actually, yes. There is a guide on the Arch wiki on how to seperate the headphone jack on the front of the computer from the speaker jack on the back so that you can move streams between them and put different stuff on them. Quite convenient.


              Also, this thread is about ALSA, why are you asking about PA features?

              Comment


              • #8
                Originally posted by phoronix View Post
                Phoronix: ALSA: Audio Compression Offloading, Power Savings

                Besides lots of graphics talks at the GStreamer 2012 Conference, the Advanced Linux Sound Architecture (ALSA) was talked about with a status report and mentions of some features soon to be landing in future Linux kernel releases...

                http://www.phoronix.com/vr.php?view=MTE3MTQ
                Hmm, if these things happen it duplicates it good bit of the things PA does (wall timestamps, output redirection (just jack for the time being, but that was, and in particular, one of the advantages PA brought)). I wonder if this includes that pll/dll work that was mentioned in another thread(admittedly that is driver, and rather than ALSA, specific).

                Comment


                • #9
                  Originally posted by uid313 View Post
                  Does PulseAudio do bit-perfect playback?
                  I believe PA resamples everything to a predefined samplerate (see /etc/pulse/daemon.conf), so if your source material does not have the same samplerate, it is by design not bit-perfect.

                  Comment


                  • #10
                    Originally posted by thofke View Post
                    I believe PA resamples everything to a predefined samplerate (see /etc/pulse/daemon.conf), so if your source material does not have the same samplerate, it is by design not bit-perfect.
                    The SoundBlaster Live! resampled everything internally to 48 kHz.
                    People were pissed.

                    Now when PulseAudio does it, its okay?

                    Comment


                    • #11
                      Originally posted by uid313 View Post
                      Now when PulseAudio does it, its okay?
                      It doesn't.

                      Alternate sample rates

                      A lot of common (desktop) hardware supports multiple sample rates. Interesting, among these, are 44100 Hz and 48000 Hz, since all common sample rates can be expressed as a simple multiple of one of these, which implies cheaper resampling, when it is required. Previous versions of PulseAudio only supported opening the device at a single sample rate, requiring all streams that did not match this rate to be resampled. We now support switching the device's sample rate dynamically at run time, allowing us to avoid resampling, or reduce resampling overhead. This should result in CPU and power savings on hardware that supports such switching (most Intel HDA-based devices at least).
                      -Source

                      Comment


                      • #12
                        Originally posted by Teho View Post
                        It doesn't.

                        -Source
                        So I just play a music file and it will be bit-perfect?
                        How do I do bit-perfect playback?

                        Comment


                        • #13
                          as far as looking if your audio gets resampled, you can check that by checking the cpu usage of the program that the sound goes thru
                          (some is used just to transfer the data, alot more is used for resampling; how much depends on your cpu ofc)
                          idk much about pulseaudio, but common sense tells me you'd have to resample all audio to some common frequency and bit rate

                          on most sound cards the signal gets resampled anyway

                          as for the things written on boxes:

                          dolby surround is a format for multi channel audio mostly used in dvd's
                          eax is a proprietary protocol for 3D audio (yes, proper 3D audio is science and takes a little computing power, eax is an engine on creative sound blaster cards)
                          most modern sound processors on cards support things like openal and others for 3D sound positioning, but im having my doubts as to how much is implemented on the software side in linux drivers/sound API's
                          eax and things like that need to be supported in your game too, they rarely are

                          most modern cards have mp3/flac/aac/etc decoders in their chips, but again they have to be written in the driver to be used
                          only things you can read from a card and be sure it means something usefull is sampling rate/bit rate (but again you probably dont have music/games that go above 48khz/16bit so it dosent rly matter)
                          and S/N ratio (signal to noise ratio, and i see lots of those data manipulated or just plain faked)

                          most other things written are just bullshit

                          interesting thing to know; best surround youl get is from headfones
                          yes, i know it sounds dumb getting best surround from a stereo source, but when you look at it you have only 2 ears
                          and the way we recognize where the sound is comming from is by its phase (and thats what 3D positioning means basicly)

                          PS mp3/ogg/aac etc (and games use them or similar) are faaaaar from the original
                          they use "psychoacoustics" too cut out a part of the sound spectrum that you probably wont notice missing
                          that woudnt be bad at all if properly encoded, but almost all i found is just wrong either by the person encoding it(check "loudness wars" for an example) or by the fact that your sound source(speakers and all else in the chain, mostly speakers) isnt perfect

                          for example you have a DnB song with vocals;
                          when the bass gets loud, the mp3 encoder presumes you wont hear a part of the vocal
                          and it would be right if your sound source could put out bass that loud(and in phase), but it cant
                          so the vocal you can hear clearer then you should(since the bass aint that loud) you hear "zooming" in and out

                          if you want a good sound card i recommend a cheap asus xonar (DS/DX, whatever is cheaper) since i found they have professional quality sound (i say professional quality sound, not that they are professional quality; but they still ALOT better then all in the price range)
                          Last edited by gens; 08-30-2012, 09:07 AM.

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                          • #14
                            Originally posted by uid313 View Post
                            So I just play a music file and it will be bit-perfect?
                            How do I do bit-perfect playback?
                            You set it up so whatever sample rate your music is in is specified as an alternate sample rate and make sure that the audio stops before something else with a different sample rate.


                            Also, bit perfect isn't nearly as big a deal as people in this forum seem to think.. So long as you select a halfway decent sampler it won't degrade your audio perceptibly.

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                            • #15
                              Seams any topic can be made in to a discussion about PA. Also isn't all this answered in the manual, except for the stuff that is relevant for media players and not sound servers.

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