DragunR2 wrote:
Why is DTS-HD preferable? I thought LPCM was uncompressed.
Being compressed in itself is not bad or an issue and being uncompressed is not what makes the audio better. Being lossless is what makes the audio better. It is important to understand that 'Lossless' does not mean 'Uncompressed' and all 'Compression' is not 'Lossy'. In the computer software world, all zip, rar etc. files are compressed but are lossless. In other words when you uncompress them, you are able to retrieve an exact replica of the original without any loss in data. Similiarly, both 'DTS HD Master Audio' & 'Dolby True-HD' are compressed but are still fully lossless formats. You may wonder, that since LPCM is also lossless, then why not just stick to it, the answer to that is quite simply the fact that LPCM, due to it being uncrompressed, unneccesarily takes up far more space on the disc and that too without any advantage or gain in audio quality over DTS-HD Master Audio or Dolby True-HD. The only reason to use LPCM would be to save on royalty costs involved with using the HD audio formats.
Blu-Ray HD Audio Options:
DTS-HD Master Audio:
Output via HDMI v1.3- 'Dolby True-HD' full lossless Bitstream (Digital) / Full lossless multichannel LPCM (Digital).
Output via HDMI (versions older than v1.3) - Full lossless multichannel LPCM (Digital).
Output via SPDIF/Coaxial - Standard 1.5mbps 'DTS' lossy Bitstream (Digital).
Output via Analog outs (If the player has inbuilt decoding of the HD audio formats) - Full lossless decoded 7.1/5.1 analog audio
Output via Analog outs - Downmixed stereo analog audio.
Dolby True-HD:
Output via HDMI v1.3- 'Dolby True-HD' full lossless Bitstream (Digital) / Full lossless multichannel LPCM (Digital).
Output via HDMI (versions older than v1.3) - Full lossless multichannel LPCM (Digital).
Output via SPDIF/Coaxial - NO digital Bitstream.
Output via Analog outs (If the player has inbuilt decoding of the HD audio formats) - Full lossless decoded 7.1/5.1 analog audio
Output via Analog outs - Downmixed stereo analog audio.
'DTS-HD Master Audio' takes the original master and splits the data into two sets of data, one is the 'core' lossy stream and the second is the balance of the original data. If your receiver/pre-pro does not support 'DTS-HD Master Audio', it simply decodes the 'core' and gives you regular 1.5mbps DTS. If the receiver/pre-pro supports 'DTS-HD Master Audio' it reads and adds the 'second stream' of data to the 'core' stream and recreates the original bit for bit recording. The 'core' part of 'DTS-HD Master Audio' can be passed via SPDIF, thus making 'DTS-HD Master Audio' fully 100% backwards compatible.
'Dolby True-HD' on the other hand, although lossless, is not backward compatible. 'Dolby Digital Plus' works similiar to 'DTS-HD Master Audio' and is fully backwards compatible with 'Dolby Digital', but it is not lossless and is only slightly superior to 'Dolby Digital'.
The difference between the two audio formats, is in the fact, that in the case of 'DTS-HD MA', the player will also extract & output the standard 1.5mbps 'DTS core' bitstream via the digital SPDIF/Coaxial output, which it cannot do in the case of 'Dolby True-HD'.
In conclusion, if it were not for economic politics, all we need is a single 'DTS-HD Master Audio' track on all Blu-Ray discs. Universal Studios, Fox & MGM have quite sensibly taken this approach and they offer only a single 'Primary language' track in 'DTS-HD Master Audio' on all their BDs. Why Warner insists on using 'Dolby True-HD' is a mystery to me, since they then have to also put a second 'Dolby Digital' track for backward compatibility. But then again, this is Warner we are talking about. In actuality in more cases than not, their solution is to simply do away with the 'Dolby True-HD' track and have a single lossy 'Dolby Digital' track.
By the way, in case your receiver/pre-pro is not equiped to decode the 'DTS-HD Master Audio' or 'Dolby True-HD' data, all Blu-Ray players can derive a full lossless multichannel LPCM and output the signal via HDMI. Do keep in mind that a LPCM track is still digital and thus cannot be sent via the analog outputs.