SACD ISO Patcher & reauthor

• Every channel layout the standard allows - all ten of them. Five channels can now become a five-channel disc or a six-channel one with the bass silent, and the picker says which is which.
• Channels can be swapped. Choosing a place another channel holds makes the two change places, so any arrangement is reachable; the button beside them puts the program's proposal back.
• Picking a different layout moves the channels with it. At 4.1 the third channel becomes the LFE, and every list on the screen agrees.
• Building a disc no longer breaks off halfway because of channel names. Files that name their channels C000, C001 ... - what sox_ng and others write - are placed correctly and stay that way; if a placement really is missing, it is said before the compression, not after it.
• The channel table no longer passes a guess off as something read, and no longer asks you to place channels it has already placed correctly.

I wrote it for myself. I like keeping my large SACD collection as disc images, and I kept running into the same wall: the music was there, in DSD, and there was no way to put it back into the shape a disc has - not without a studio tool priced for a studio.

The DST packer here compresses better than a good many proprietary ones, so I re-author rips I already have and save a great deal of space doing it.

Having done the work, I am glad to share it with the audiophile community.

An SACD is not a folder of tracks. Around the music sits a structure the format prescribes down to the sector, and everything below comes from the Scarlet Book specification that defines it. A disc is playable only if that structure is right - which is why authoring is a job for a program rather than a copy command.

The tables of contents. The Master TOC exists in three identical copies, at logical sectors 510, 520 and 530 (spec 2.2.4). Each audio area is built as Area TOC-1, then the Track Area, then Area TOC-2, and Area TOC-2 is a copy of Area TOC-1 (spec 2.2.6). reauthor writes all of them, and writes them consistently: a disc whose own tables disagree is a disc some players read one way and others another.

The text. Album, disc and track text lives in those tables, one block per text channel, and a disc may declare up to eight channels - eight languages, each in its own character set (spec 1.7.2.8.1). Every declared channel must carry at least one text item (spec 1.7.2.8), so an empty language is not a cosmetic problem: it makes the disc invalid, and the program says so before the build rather than after.

The audio. Input is DSD64 in .dsf or .dff, one file per track, or a single DSDIFF Edited Master carrying the whole disc. The Multichannel area is always lossless-compressed: "The audio information in the Multi Channel Area must be DST coded DSD" (spec 2.2.6.2.6). For the Stereo area compression is your choice - plain DSD is simplest and largest, DST is smaller and bit-identical. A last frame that is not full is completed with silence rather than cut short, so the disc never ends mid-frame.

The channel roles. Which channel of a multichannel file is the centre, and which the bass, is worked out from the sound itself - because the file often does not say, or says it wrong. The program shows you what it found and lets you overrule it before anything is written.

Before you get a file. The project is checked against the standard first. The build then encodes, assembles the image, and reads the finished file back to check it again - and if anything does not match, no file is produced. A build you cancel leaves nothing half-written, and an existing image is never replaced without your say-so.

• The "Bring to standard" button repairs more faults: a seek table that no longer matches the audio, a wrong area table-of-contents size in the disc's file list, and an empty language left behind.
• A disc that declares the wrong character set is now spotted - German titles with letters the declared set does not have, say - and a "Fix the character set" button beside the language sets the right one without touching a single title.
• Scanning a folder has a new filter, "Can be brought to standard", so the discs that button can help are visible at a glance.
• Folder and file names for extraction are yours to set: sixteen variables with a live example beside them, the names shown before the extraction starts, and a warning about a path that is too long.
• Extracted files are checked afterwards - one line with the result, and a link that opens the details and the tags.
• Help now lives in a side panel behind one [?] button: it opens on the section you need and does not cover the fields you are working in.
• Cover art is saved whole, and tags are read from .dff files too, not only from .dsf.
• A backup made by the backup command can be restored again, and the backup manifest carries the right program version.

Like most useful tools, this one was born from irritation.

Some music-player libraries are pedantic in the worst way. Write the same artist in two different letter-cases on two discs - Keith Jarrett here, KEITH JARRETT there - and they will quietly file them as two strangers who happen to share a name, scattering one artist across your collection.

And then there are the discs themselves. Many early SACDs arrived almost mute: no track titles, a missing year, an absent catalog number, a performer left off entirely - just Track 1, Track 2, Track 3 where a whole program of music should be.

You could re-rip and re-author a multi-gigabyte image to fix a single typo - or you could reach inside the disc image and correct the words directly, leaving every audio sample exactly where it was. That second idea became SACD ISO Patcher.

An SACD keeps its words and its music in different places. The text you see on a player - album, disc and track titles, artists, publishers, copyright - lives in tables of contents, not interleaved with the audio. That separation is what makes editing in place possible at all, and everything below comes from the Scarlet Book specification that defines the format.

Album and disc level. The Master TOC Area holds three identical copies of the Master TOC, stored at logical sectors 510, 520 and 530 (spec 2.2.4). The text itself sits in a structure called Master_Text, and its size is exactly one sector per text channel (spec 3.1.2). A text channel is one language: a disc may carry up to eight of them (spec 1.7.2.8.1), which is why the same album can show Latin titles to one player and Japanese to another.

Track level. Each audio area - the stereo one, the multichannel one - is built as Area TOC-1, then the Track Area, then Area TOC-2, and Area TOC-2 is a copy of Area TOC-1 (spec 2.2.6). Track titles and credits live in a Track_Text block inside those area tables. Each track may carry at most ten text items per channel (spec 3.2.6.3), which is what limits how many separate fields - title, performer, composer, arranger, message, copyright and their phonetic variants - a single track can hold.

Why the audio is never touched. The Track Area, where the DSD audio actually is, takes no part in a metadata edit. Rewriting a title changes bytes in the tables of contents only. Nothing shifts, nothing is re-encoded, and the audio sectors keep their exact positions - which is why an edit takes seconds on an image of several gigabytes instead of the hours a re-authoring run would need.

Why copies matter. Because the format mandates duplicates - three Master TOCs, and Area TOC-2 mirroring Area TOC-1 - a naive editor that rewrote only the first copy would leave a disc whose own tables disagree with each other. Every copy has to be updated together, or the result is a disc that some players read one way and others another.

What happens when you press Save. Before a single byte is written, every sector the change will touch is copied into a backup file. The write is then all-or-nothing: either the whole edit lands or the image is left exactly as it was. Afterwards the image is read back and compared against what you asked for, so a save that silently went wrong cannot pass unnoticed. A backup that could not restore the original byte for byte is refused rather than written - the point of the program is that an irreplaceable rip survives it.