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Bitperfect change directory1/6/2024 ![]() A somewhat crude invocation to see if the system's default output configuration to a set of 5.1 surround sound speakers is working would be: You can use ALSA's speaker-test utility to perform output tests to determine if your speaker and sound configurations are correct and functioning properly. See also PulseAudio's website on how to setup your computer and applications for PulseAudio. Whilst this is faster than other sound servers it is unacceptably slow compared to direct interaction with alsa and can cause significant problems with video playback. High latency, sound samples can take anywhere from half a second to 2 seconds longer to reach the sound card.sound output on different computer is possible. and last but not least network transparency, i.e.abstraction of hardware, including autodetection of soundcards via HAL, moving from one output to another without restarting the application and using multiple sound cards together to output more channels.management of all sound applications in one place using GUI tools.volume settings (mixer) specific and stored per application.PulseAudio is a sound server, whose advantages are Support for PulseAudio was added in MythTV 0.23. Several Linux distros (Ubuntu, Fedora) now use PulseAudio per default. Otherwise the modern ALSA does software mixing by default and resamples to 48k before sending data to the card.įor the vast majority it's far better that we resample - SRC anywhere else in the chain (ALSA, card) would be done with a SNR much less thanĮcho "insert into settings values ('DisableResampler', 0, '')" | mysql -u mythtv -p mythconverg Now when you play a CD your amp should show PCM output at 44.1 kHz, and TV broadcasts as PCM at 48 kHz, and your DVDs will also have full blown surround.ĭon't forget to rip your CDs using Lossless FLAC as the encoder (this is the default for the "Perfect" setting in the MythTV) will preserve the 44.1 kHz audio files from your CDs.Īn option was added in version 0.22 ( thread): if you're confident that ALSA isn't going to resample (twice) and have appropriate hardware, you can add a setting 'DisableResampler' with value 1 to the database. With most modern Linux distros there is not a need to mess around with the ALSA configuration filesĭon't forget to unmute your iec958 output using alsamixer. On Mythfrontend Utilities/Setup->Setup-General go to the Audio page and set your audio device asĪudio output device = ALSA:958 So just configure this device as the audio device in MythTV. The device name for this connector is typically "958". This is very easy to overcome, by sending all your audio directly to your soundcards SPDIF or IEC958 Connector. The upsampling in ALSA is unfortunately very low quality, and if you have a half decent amplifier and speakers, you will notice that CD playback has a congested compressed sound to it. ![]() ALSA typically takes the sound from your content, routes it through a module called "plug" where this resampling takes place, and then routes it to a module called "dmix", a software mixer, before it outputs it to your SPDIF/iec958 connector.įor Die hard Audiophiles, this resampling is a real source of irritation as CD audio is made using PCM at 44.1 kHz. This keeps it compatible with TV broadcasts as well as Dolby Digital and DTS surround on DVDs. You need to be aware that ALSA by default will upsample all of your audio to 48 kHz. We want to play DVD with full surround sound using DTS or Dolby Digital. We want to have the audio decoding done outside of the computer for greater sound quality.Ģ. For MythTV installations it is advisable to turn off any sound servers that sit on top of ALSA such as Pulse Audio or the KDE or Gnome sound servers.ĭigital sound is the preferred method to get audio from a MythTV installation for two reasonsġ. The default in modern Linux systems that use the 2.6 kernel is now ALSA. If you have additional information, please add it to the External Links page. The MythTV wiki Sound card page also contains useful information on this topic.
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