Initial pile-audio

crates/pile-audio/tests/files/flac_subset/README.md

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+# Group subset
+
+The FLAC format specifies a subset of itself to ensure
+streamability and limits the decoding requirements for hardware
+implementations. The reference FLAC encoder will enforce this
+subset unless specifically disabled.
+
+The files in this group are considered a baseline for general
+decoders: these files should be properly decoded or properly
+rejected before playback is attempted by any decoder. A
+decoder can choose to reject certain files, for example
+multichannel files, files with high or unusual samplerates,
+files with a high bit depth. Crashing or mangled playback of
+these files is probably going to be noticed by unsuspecting
+users of a decoder. Read the README.txt in the directory
+subset for details on each file.
+
+
+## Files \#1 - \#27
+
+The first 10 files tests 44.1kHz, 16-bit audio with various
+blocksizes that are within subset.
+
+Files 11 through 23 tests the ability to decode FLAC files
+with various features that are within subset but aren't used
+often.
+
+- File 11 uses the maximal allowed rice partition order (8)
+- File 12 uses the maximal allowed qlp precision (15)
+- File 13 uses the smallest sane qlp precision (2)
+- File 14 uses wasted bits
+- File 15 uses only 'verbatim' frames
+- File 16 uses rice escape codes and partition order 8
+- File 17 uses all possible fixed orders (especially order 0 which isn't used often)
+- File 18 is encoded with precision search, using qlp precisions between 3 and 15
+- File 19 uses a samplerate of 35467Hz
+- File 20 uses a samplerate of 39kHz
+- File 21 uses a samplerate of 22050Hz
+- File 22 has 12 bits per sample
+- File 23 has 8 bits per sample
+
+Files 24 through 27 test the ability to decode a FLAC file with
+a variable blocksize. This is a subset feature which is
+currently (August 2021) only implemented in the Flake decoder
+and its forks/decendants and is not enabled by default.
+
+With the release of FLAC 1.2.0 in July 2007, the FLAC
+specification was augmented to more clearly signal variable
+blocksize streams by the use of a special bit in the header.
+File 24, 25 and 26 use this format. File 27 follows the old
+specification, which is much harder to detect
+
+- File 24 uses the current format and is created by flake r264
+- File 25 uses the current format and is created by a modified flake r264 creating smaller blocks
+- File 26 uses the current format and is created by CUETools.Flake 2.1.6
+- File 27 uses the old format and is created by flake 0.11
+
+## Files \#28 - \#37
+
+Files 28 through 37 test the ability to decode various
+high-resolution FLAC file (96kHz, 24-bit)
+
+- File 28 uses default settings
+- File 29 uses the largest allowed blocksize (16384)
+- File 30 uses non-standard blocksize 13456
+- File 31 uses only 32th order predictors
+- File 32 uses escape codes and partition order 8
+- File 33 is upsampled to 192kHz
+- File 34 is upsampled to 192kHz, uses blocksize 16384, 32th
+    order predictors only, maximum LPC precision and maximum
+    partition order
+- File 35 uses non-standard samplerate 134560Hz
+- File 36 is upsampled to 384kHz
+- File 37 has 20 bits per sample
+
+## Files \#38 - \#44
+
+Files 38 through 43 test the ability to decode various
+multichannel FLAC files. Each file contains a voice description
+of the channels present, so as to see whether the channels are
+decoded in the correct lay-out.
+
+- File 38 is 3.0-channel (left, right, center)
+- File 39 is 4.0-channel or quadraphonic
+- File 40 is 5.0-channel
+- File 41 is 5.1-channel
+- File 42 is 6.1-channel
+- File 43 is 7.1-channel
+
+File 44 tests the ability to decode a file with the highest
+possible data input per second, staying within subset and using
+a standard samplerate. It also only uses 32th order predictors
+at the highest possible predictor precision and the largest
+blocksize allowed within the FLAC subset making it especially
+challenging to decode.
+
+## Files \#45 - \#59
+
+Files 45 through 59 test the ability to handle various streams
+with valid but rather unusual or extreme metadata.
+
+- File 45 has 'unknown number of samples' in STREAMINFO
+- File 46 has maximum and minimum framesize set to 'unknown'
+- File 47 has only a STREAMINFO block
+- File 48 has an extremely large SEEKTABLE
+- File 49 has an extremely large PADDING block
+- File 50 has an extremely large PICTURE block (JPG of 15.8MB)
+- File 51 has an extremely large VORBISCOMMENT block
+- File 52 has an extremely large APPLICATION block
+- File 53 has a CUESHEET block with absurdly many indexes
+- File 54 with the same 20 VORBISCOMMENTs repeated 1000 times
+- File 55 has the metadata of track 47-52 combined
+- File 56 has a PICTURE with mimetype image/jpeg
+- File 57 has a PICTURE with mimetype image/png
+- File 58 has a PICTURE with mimetype image/gif
+- File 59 has a PICTURE with mimetype image/avif
+
+## Files \#60 - \#64
+
+Miscellaneous, later additions
+
+- File 60 is mono audio
+- File 61, 62 and 63 are signals with rather extreme
+    characteristics that might trigger overflow if a decoder
+    uses 32-bit integers to calculate the predictor where 64-bit
+    integers are appropriate
+- File 64 contains rice codes with escape code zero