Tutorial MCH Music, SACD options and ISO/DSF/DFF file formats

Discussion in 'HDD Media player(RTD 1296)' started by Nice Monkey, Jul 9, 2020.

  1. Nice Monkey

    Nice Monkey Well-Known Member Beta test group

    Introduction to the SACD disc basics and options
    SACD discs are commonly Hybrid with a normal CD player first layer for backward compatibility playback on ordinary CD-players and a second SACD layer (DVD type data layer) for SACD playback in DSD64 1-bit sample format on specifically SACD capable players.
    There are a few DSD128 and even fewer DSD256 original studio SACD's with higher sampler rates.

    The SACD layer has mostly 2CH (=Stereo) tracks but may optionally have MCH (=Multi Channel 5.1) tracks additionally. So a HW based SACD player lets users then select CD, 2CH or MCH playback for those albums having all three on them. The exact content/playback capabilities are always displayed on the disc and labels accordingly. To make bigger contents fit on the SACD layer this may be compressed using DST (Direct Stream Transfer). MCH SACD albums always use DST compression to make them fit on the DVD layer. SACD's sales almost came to a hold with just a few small labels still producing them for a very specific audience.

    Truly enjoying MCH music and SACD playback!
    SACD was maybe developed and marketed too early in time by Philips/Sony. Producing DAC's that could handle the DSD format well did not really exist yet and very few people having a quality 5.1 audio setup to truly enjoy MCH. This caused a lot of debate if DSD was really superior to PCM (CD <=> SACD). Now 30 years later this all changed as not only the quality of the DAC's and AMP's improved but also the clock circuitry used with it made many improvements steps. The accuracy and phase jitter of the clock oscillators feeding a DAC was found to play a huge role in sound reproduction. For the excellent SACD format it seems that these innovations just came too late which is a real pity as the quality difference is a lot easier to perceive. With my setup all visitors can hear it doing A/B blind tests.

    It is my practical experience that you can only squeeze out maximum MCH 5.1 sound quality using a consistent choice of speakers (same brand and even model range). Using a mixed bag of speakers for front, center and back channels never gives satisfactory audio results. It may result very acceptable for movies (getting those effects) but definitely not for top quality music reproduction. I know it is a big temptation to use simpler/cheaper speakers for center and back channels, but frankly you should not do so when targeting for MCH 5.1 music listening too. Learned it myself the hard way changing my speaker setup in various steps.
    Really love the MCH sound on various SACD (DTS-CD/BD) music albums now. On some regular CD's the DSP provided up-scaling to DTS/THX 7.1 with my HT AMP produces pretty nice results too.

    There is a curious parallel between MCH music and 3D Video as both formats keep disappearing and making a come back with a newer technology. For music we first saw Quad LP, next MCH SACD, DTS-CD, DVD-Audio, BD Pure Audio. Now only BD Concerts with occasionally MCH DD/DTS audio tracks on them are actively produced by the big labels. Came across a curious collection of Quad LP recordings transferred by a studio to DTS-CD's which sound amazingly well this despite the age of the original recordings.

    ISO/DSF/DFF files
    Ripping an SACD results in an SACD ISO container with the DVD layer content only. The CD-layer is never part of it. Obviously that layer can be ripped using normal DAE (Digital Audio Extraction) tools if desired too. The SACD ISO contains all 2CH and/or MCH DSD tracks with or without DST compression as the final result. It is not possible to distinct the various options used without opening the container.

    - Individual tracks can next be extracted from the full SACD ISO in DSF or DFF file format. Both are maintaining the original DSD 1-bit sampling format of the ISO. DSF (Sony) does not facilitate DST compression but DFF (Philips) does optionally. Having a DSF track you can be sure it is not compressed with DST anymore and only DSF supports tagged meta data making it the most popular extraction format.
    - SACD ISO's with just 2CH tracks on them are mostly not DST compressed but when combined with MCH also those 2CH tracks are always compressed to reduce the total disc size. A MCH album would be 4x the size of an equivalent 2CH album without using DST compression!
    - MCH albums have also 2CH tracks on them but there are a few very rare exceptions known (mostly classical concerts it seems). 2CH and MCH tracks hence need to be extracted individually. You can't see if a DSF or DFF file is MCH or 2CH and neither if a DFF file uses DST compression or not. If all Stereo (2CH) tracks aren't very short but the album is still around 1 Gbyte (ISO or DFF's) then it probably is DST compressed.
    - It takes roughly 3x the total duration to extract a DST compressed SACD ISO to DSF or to DFF with DST decompression selected versus direct extraction to DFF with DST left untouched. MCH is 3x 2CH regarding size and it takes proportional resources to extract those tracks. So extracting a MCH DST track takes 9x the processing power compared to a 2CH uncompressed track! This is important to realize as it all needs to be done real time using media players in software which many can't cope with or not cope with well resulting in distorted playback if supported at all.
    - DST is indeed very effective in size reduction (album reduced with roughly a factor 2.5). But even using DST some long MCH albums may still not fit on a single DVD layer. These then use both DVD layers for just the SACD tracks skipping the Hybrid CD compatibility layer as the consequence. Not a very common format but have a few of those myself (resulting ISO > 4.7 GByte).

    Media player (restricted) SACD/DSD capabilities
    Most (Android) music player platforms and player APP's don't support DST at all or are not doing the decompression well real time. This is often not stated clearly as DST in fact is hardly ever mentioned at all anywhere and is e.g. never indicated on the SACD disc or labels. Some HW based players may NOT support MCH tracks for exactly that same reason without stating so explicitly.

    Music players claiming support for SACD/DSD will all at least be capable to playback DSF files and will mostly also play uncompressed DFF files. Many have problems with compressed DFF and only a very few can handle (compressed) ISO's correctly. Standardizing on DSF is therefore a popular method for many, this despite the far bigger size compared with compressed ISO/DFF. Personally I always only keep the original ISO's with just the converted MCH FLAC tracks added for the MCH SACD albums specifically as that is my only way to play those now (beyond playing the original physical discs).

    Media players unfortunately don't support native DSD output via HDMI and/or Analog output and will convert DSD streams to PCM streams real time when being played. Only HiFi media players with advanced onboard DAC's will output DSD directly when switched to Analog Output using such DSD capable DAC.

    Only a few media players like Zidoo can (or will try to) play MCH ISO's but in fact playing then the 2CH tracks. But also Zidoo Music Player has distortion problems playing MCH ISO's when converting these to 2CH PCM via HDMI specifically due to the need for DST decompression. Using X20 Pro and UHD2000 HiFi models there are no such performance problems anymore. When switching to DAC Analog output the need for DSD=>PCM conversion disappears which reduces the processor load enough to get into the safety zone.
    There are currently no Android based HiFi media players supporting MCH DAC's so that method restricts output to 2CH (Stereo) playback only.

    Also playing MCH FLAC one may run into CPU limitations as going above 88.2/96 kHz sample rates with 24-bit depth may already start to produce distortions.

    The new RTD1619 based media players are maybe capable to do MCH DSF => MCH PCM output as that total load is only marginally above MCH SACD/DSD ISO => 2CH PCM playback. MCH SACD/DSD ISO => MCH PCM most likely remains far out of reach. Uncompressed MCH DFF on the other hand should be possible as that is similar load to MCH DSF. Using appropriate drivers MCH DSD via HDMI could potentially work too?

    Corrections, comments and questions are as always very welcome.
    Last edited: Jul 10, 2020
    gymnos, pcristi and McBluna like this.
  2. lexalalex

    lexalalex New Member

    new firmware for "Dune HD Pro 4K II" can decoding of multichannel SACD audio files which use DST compression (DFF and ISO) to multichannel PCM.

    - New feature: Pro 4K II model: Added support for decoding of multichannel
    SACD audio files which use DST compression (DFF and ISO) to multichannel
    PCM. Now, such files can be played with multichannel PCM output to HDMI.
    A new setting "Setup / Playback / Parameters / Preferred SACD area" can
    be used to choose, for images, which contain simultenously multichannel
    and stereo variants, which variant to use (default is Multichannel).
    (NOTE: not supported on older Realtek models, because CPU power of older
    models is not enough for stable playback.)

    - Improvement: Realtek models: Added support for playback of very large
    (very long) audio files in various lossless formats (SACD DSF/DFF/ISO,
    FLAC, APE, WavPack) (for examples, 192/24 audio file longer than 70
    minutes could not be played before, because of internal 32-bit
    gymnos likes this.
  3. gymnos

    gymnos Member

    What about Zidoo players?
  4. Reelyator

    Reelyator Active Member

    Dear Nice Monkey,
    thank you for this nice Tutorial!!

    I have several SACD-Iso´s on my NAS wich i tried to play through several Players on my X20:
    1) Zidoo Mucic Player
    2) Kodi 18.09 with the "SACD Iso Support Add-on"

    Both approaches were not very convincing.
    1) is a mess because the imoport constantly crashes. The imported files are hardly connected to the correct Albums and Artists and there is ZERO feedback from the Zidoo Support team if you ask what to to to allow the correct detection of Artists and Albums. As far as i rememnber MCH has never worked.
    2) works a bit better than 1) ~50% play correctly, the rest is just noise. The biggest bug (in the most recent version 1.0.4 of the Add-on is the fact that after installation BD- DVD- and UHD-Iso files are not detected anymore by the Kodi Video Library. MCH never worked as well. The detection of Artist, Album, Title... is a bit better than 1) but still far away from reliable. Album Names are displayed as Artists, Albums have no Artists at all, Compilation Albums (with several artists) are not imported at all....

    Summing up: The Zidoo Music Player (latest version) is useless for SACD Iso Playback. I hope the problems of the SACD Iso Support Add-on for Kodi will be worked on in the future. As the Add-on is already listed on the Matrix Repository i hope to see some updates in the near future.

    If anybody here knowns. how to modify the Media-Tags embedded in SACD-Iso´s then please let me know!
    gymnos likes this.

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