Using the Directstream for Blu Ray and DVD playback


#1

Maybe a few silly questions …

I have quite a bit of music videos such a live concerts on DVDs and Blurays (not DVD-audio or bluray audio). I have recently transferred these as ISO images onto the Mac Mini. I am using Aurora Player for playback and this does so without any problems. I can even choose the PS Audio as my audio output which is perfect … and have the HDMI from the Mac to the TV.

No doubt I think it sounds stunning hearing a huge difference (as compared to my cheapish blurry player direct into the amp) when I go through the DAC. But the sampling and the bit rate seems to be always at 96/24 for both playing back the DVD and Bluray ISO.

  1. Is this the standard rate for DVDs/Blurays

  2. Presumably there is no sonic penalty for LPCM and its fully compatible

  3. The Directstream sometimes get stuck on a certain rate - so even when I go back to JRiver to play a standard redbook file … its still stuck at 44/24 rather than 44/16 - is there a reason for this?

Many thanks

James


#2
sicklehut said
  1. Is this the standard rate for DVDs/Blurays

  2. Presumably there is no sonic penalty for LPCM and its fully compatible

  3. The Directstream sometimes get stuck on a certain rate - so even when I go back to JRiver to play a standard redbook file … its still stuck at 44/24 rather than 44/16 - is there a reason for this?


DVDs are a mess :)
  1. Digital Rights Management allows each disk played to restrict the highest sample rate that can be played from DVDs (and I presume Blurays) Typically 24/48 or 24/96, but this probably isn’t what you are encountering.

  2. Besides the same answer as question 1: Stereo LPCM may be a separate track mixed as stereo on the disk. But often the player is mixing down a multichannel mix track to stereo for you. Many DVDs are in DTS which, tho it can look like stereo LPCM is really encoded multichannel and will sound like noise when played directly, but most players can decode DTS and then provide either a multichannel PCM or more likely a stereo PCM mix. Dolby Digital can be played directly as stereo PCM without a great loss.

  3. The DirectStream never gets stuck at a certain rate or sample width: for example it never down converts 24/96 to 24/48. It always counts the number of samples seen per unit time and reports the answer if it is a standard sample rate - if not it reports —. Similarly the number of bits reported is simply a function of if a lower bit is ever non zero over a period of time: e.g. if the bottom 8 bits are always 0 it reports a 16 bit sample, if the bottom six bits are always zero but the two bits just above that are sometimes a one then it reports 18 bits… if all of the bottom bits are sometimes non-zero then it reports 24 bits.

In general if the player (or the OS) has a volume control that isn’t set to unity (100%) or is doing some digital signal processing (filtering or sample rate change, etc.) then the lower bits are often non-zero and a CD (which only has 16 bits) will be sent as 44.1/24 and so reported by the DS.

In JRiver MC you can use the Audio Path entry on the Player menu to see if JRiver is applying DSP, a volume control or other DSP to what it’s playing. If JRiver isn’t messing with the audio, then your OS must be (or if you are using a sound card to connect to the DS, it must be…)

There’s a How To that describes most of the things to check and explains how to verify that audio isn’t getting messed with on the way to the DS: http://www.psaudio.com/ps_how/how-to-run-a-bit-perfect-test-with-directstream


#3

Thank you Ted for your reply - basically answered everything I wanted to know!

Luckily the DVD and Bluray audio appears to be playing back fine and certainly sounds so much better through the Directstream. To the point its uncanny watching Jeff Beck Live in Tokyo and hearing his strat tone come through …

Cheers again 77_gif


#4

One other thought is to check your settings in Audio Midi Setup (in your Utilities folder within your Applications folder). I do not know the programs you are using for DVD and Blu-ray but if they don’t bypass Audio Midi Setup (as JRiver does), all files would be up or down sampled to what is set there (e.g., 96-24). That would be the case if you were using iTunes to play audio files without a helper program (like, BitPerect, Amarra, etc.)