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Author Topic: HD v SACD, WASAPI v Direct Sound  (Read 1492 times)

shAf

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HD v SACD, WASAPI v Direct Sound
« on: December 21, 2013, 10:59:14 am »

I just experienced a problem trying to play a SACD source whereby MC19 was required to downsample from 88.2kHz (... and presumably anything higher) to 48kHz.  If I instead configured audio output from 'WASAPI' to 'Direct Sound', MC played the SACD source fine without downsampling. 

I've never had a problem with WASAPI and HD sources from HDTracks.  What is the difference, and what am I missing with 'Direct Sound' (... including HD audio for movies (e.g., Dolby True HD, DTS HD Master).

Additional note:  I prefer to bitstream my audio output via HDMI, and allow my AVR to decode the HD audio ...

TIA ... and Holidays' Cheerios  :)
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cheerios from the Avalon Peninsula, Newfoundland

6233638

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Re: HD v SACD, WASAPI v Direct Sound
« Reply #1 on: December 21, 2013, 12:12:50 pm »

DirectSound passes all audio through the Windows mixer, so it resamples everything to a fixed sample rate. (as set in the sound control panel)
WASAPI Exclusive attempts to set the hardware rate to the input rate. If the hardware cannot play it, you will have an error. The player must handle any resampling of any formats which are unsupported - you can configure this in DSP Studio.
WASAPI Shared will only play audio which matches the sample rate set in the sound control panel, so the player must resample everything to it. If it doesn't match, you will receive an error.
 
ASIO or Kernel Streaming should behave the same as WASAPI Exclusive if you hardware supports them.
 
Additional note:  I prefer to bitstream my audio output via HDMI, and allow my AVR to decode the HD audio ...
This is not recommended for HTPC playback because the audio and video clocks come from separate sources. This means that your audio and video will never be perfectly in sync.
 
If you are bitstreaming, you have one of the following:
  • Audio and video are untouched and allowed to drift in and out of sync.
  • Audio frames are dropped or repeated to keep audio in sync with the video. This produces audible errors.
  • Video frames are dropped or repeated to keep audio in sync with the video. This produces visible stuttering during playback.

If you decode in the player, you have a fourth option; you can resample the audio in real-time to maintain sync with the video. In Media Center, this is the "VideoClock" option.
This means that you have smooth playback without dropped frames, and audio stays in sync from start to finish.
 
This should produce much better results than any of the options you have available when bitstreaming.
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nct

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Re: HD v SACD, WASAPI v Direct Sound
« Reply #2 on: February 11, 2014, 04:30:52 am »

Hi there, based on my wasapi event settings in my MC 19 and setting the bit depth to "automatic for best sound quality" i noticed that while the input was 44.1khz 16 bit from source format wav, the output became 44.1khz 32 bit using WASAPI ( direct connection). Why has that happened? Secondly is the upscaling of the bit depth to 32bit necessarily better? and lastly how could i reset such that the input equals the output in bit depth . Many thanks.
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6233638

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Re: HD v SACD, WASAPI v Direct Sound
« Reply #3 on: February 11, 2014, 04:43:36 am »

Hi there, based on my wasapi event settings in my MC 19 and setting the bit depth to "automatic for best sound quality" i noticed that while the input was 44.1khz 16 bit from source format wav, the output became 44.1khz 32 bit using WASAPI ( direct connection). Why has that happened? Secondly is the upscaling of the bit depth to 32bit necessarily better? and lastly how could i reset such that the input equals the output in bit depth . Many thanks.
It is best to use the highest bit-depth that your hardware supports. This is not "upscaling" or "upsampling".
Either the extra bits are not used and set to zero (identical to a 16-bit output) or they do get used to improve the sound quality over outputting a 16-bit signal. (e.g. if you adjust the volume inside Media Center or use DSP)
 
There is no option to automatically match output bit-depth to the input bit-depth.
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