DTS-HD Master Audio or just DTS-HD in many descriptions is a lossless audio codec by Digital Theater System. It replaces the old DTS audio (actually it extends it) and its main goal is to allow a bit-to-bit representation of the original movie's studio master soundtrack. If you are unaware with the lossless term, it is a compression method that allows you to have the exact original data from the compressed data after extraction, in contrast to lossy formats which only allows an approximation of the original data to be reconstructed. An example of a lossy audio format is MP3, while another lossless audio format is FLAC.
DTS-HD has pretty much become the standard audio track of most Blu-ray discs. That is why we will try to explain how it works, and of course, how you can rip it, in this article.
The DTS-HD Core and how the whole format works
As you can read in detail in the DTS-HD white paper the encoding process of a DTS-HD track in simple terms is the following: first the Core, which is lossy format, similar to the old DTS is being created. Then the Core is compared to the original audio and any parts found missing are being added an an extra "residual" stream. Then both streams are used to create the final DTS-HD MA track. That way in older decoders that only support the old DTS format, you just listen to the Core stream. In decoders that support DTS-HD, both the streams are being played in the same time giving you lossless original sound quality.
The advantages of this format are backwards compatibility with older decoders, smaller size of the audio track than using both an HD and a Core track and faster encoding.
What do you need to rip
First of all I assume you have at least a 5.1 sound system, otherwise you should just downmix to stereo. Now since there are only a few software decoders for DTS-HD and these at insane prices we can pretty much assume the following scenarios:
- If you have bought a software decoder or have a decoder that supports DTS-HD and you pass-through the audio through HDMI or Optical, just create an mkv file and maintain the original audio track from the Blu-ray.
- If you decode through your PC or you passthrough to a decoder that doesn't support DTS-HD you don't need both streams. Even if you keep the whole track, you will only listen to the Core, so just keep that and remove the HD audio. For instance, you might be able to decode DTS-HD in your PC but instead you pass-through the audio to your decoder via an optical cable. Your decoder will just play the Core.
- If you want to maximize compatiblity or reduce the size of the audio track you can convert to AC3 audio in a lower bitrate.
- If you are copying a Blu-ray to AVCHD, check your Blu-ray player's manual. If it supports (most likely it will) DTS-HD keep it, otherwise follow one of the options above.
- Of course if you are converting to mkv in order to store your movie, keeping the DTS-HD format is a good idea. It will be easy to decode soon enough in any PC so take a minute and think about what you need.
Just to add my experience since I recently bought a DTS-HD sound system, if you listening to your movies in low - normal volume you really can't tell any difference between the lossless DTS-HD and just the Core. If you starting increasing the volume, especially in action films you can tell some difference, but as the DTS-HD whitepaper says the Core is also a very capable lossy format and given the huge bitrate of 1500kbps that it usually uses, in most cases you are fine just ripping the Core.
What various ripping programs support
- Ripbot264 supports getting the Core stream. Just select Core when you import the Blu-ray and then copy stream in order to get the original Core audio. You can also demux the whole stream to Wave and then use Aften to convert to AC3.
- Handbrake also supports copying the Core stream. Choose the mkv container and in the audio options add DTS passthrough.
- Staxrip can get both streams if you select the DTS-HD option or otherwise rips just the Core if you select DTS. Using the Just Remux option you get the original DTS-HD or DTS Core streams in your mkv file and you can also convert to AC3. This is my program of choice due to the many and clear options of you for audio (just demux and remux, re-encode etc)
- DVDFab Blu-ray Ripper rips both streams by default, unless you select the Remove HD Audio option which just rips the Core. It can convert to AC3 as well.
- Generally eac3to can deal with all those formats and give you any output you wish, Core or HD, just demux or recode to wave, flac etc. Then, you just mux the sound with your video file.
You can always get the original DTS-HD track by manually demuxing the Blu-ray, converting just the video with any encoder and then remux using mkvmerge using the original .dtshd track.
What if I want to decode DTS-HD
You have to buy a commercial software that contains a decoder. Arcsoft Total Media Theater 5 should install a system-wide filter that will decode DTS-HD using eac3to, Staxrip, Ripbot264 and other programs.
What about Dolby TrueHD
Dobly TrueHD is the format competing with DTS-HD. It is less common but you will surely eventually buy a Blu-ray disc that uses TrueHD as the main audio format. Well, pretty much everything above applies for TrueHD as well with the exception of the software decoder which is free and included in ffmpeg. So you can decode the lossless part just fine and use it as a source for all your encodes. Most TrueHD streams also contain an AC3 stream (kind of like the Core DTS has). Staxrip can deal with that and either remove it or extract it. (you probably want to remove it anyway)
That's about all the info you will need regarding DTS-HD Master Audio. If you have more questions just use the comments form below.