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2014-07-01, 17:03
(This post was last modified: 2014-07-01, 17:04 by axlt2002.)
Hi All,
I currently set my audio output device (Optical S/PDIF) in WASAPI mode in order obtain the so called bit-perfect music playback (i.e. the source audio stream is passed as it is to an external DAC through the selected audio device). However, in several and quite old posts, I have red that XBMC seems to manipulate in some way the stream, so no real bit-perfect...others, at the same time, are saying that set WASAPI is the way to go for it.
My first question is: which is the real status on such point?
Secondly, looking at the settings, I do not understand the meaning of "Output configuration" and "Resample quality" options. Can someone explain them to me esepcially in case of using WASAPI? Should such options be irrelevant if WASAPI is enabled? Why then is possible to modify them?
Looking forward for the usual kind support! Thansk in advance!
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A small addition: even if in WASAPI mode, when I try to change the volume inside XBMC through + or - keys, this affects the playback. I was expecting that if WASAPI is used, the only way to change the volume would be through the external amplifier...where Am I missing the point?
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First of all bit-perfect does not mean pass through the decoded stream. We distinguish between
1)
passthrough the decoded stream
This mode can be configured for WASAPI as well as other drivers. You have to enable passthrough and the codecs the receiver a capable of. In this mode XBMC can't manipulate the stream because it is decoded.
2)
pcm
Note that pcm can still be bit-perfect. If you don't apply any resampling or deamplification, pcm is bit-perfect because the decoding process itself does not have any impact on this.
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I am not aware of any receivers which can decode ALAC or FLAC so XBMC (ffmpeg) needs to do the decoding: Option 2.
In order to avoid deamplification set XBMC's internal volume to 1.0. This is maximum.
There are some situations which require a resampler, i.e. if you play a file with 48khz and the following file has 44.1. Gapless requires that the following stream uses the configuration of the previous. If we reconfigured the audio output device, there would be a noticeable gap. If you set output configuration to "best match" XBMC will try to reopen the device to match the stream properties. Means if you want to avoid resampling in this case, set to "best match" but be aware that this ruins gapless.
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Thanks a lot FernetMenta for your reply! Now is all clear!
Just one more hint on your side: no way to have the volume set to 1.0 as a default value every time XBMC is started? Or there could be a way to automatically set it to 1.0 when starting to play music files? In fact, lets suppose to watch a movie that requires to decrease the volume, it would be more efficent not take care about returning it to 1.0 every time I would start to listen music afterwards (or when I start XBMC and the value was set less than 1.0 during the previous "session" of XBMC).
Have a nice evening!
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I have never thought about this use case. On my living room box I haven't change XBMC's internal volume in 4 years. You can write a simple script and change volume via the api after xbmc has started.