64 lines
2.5 KiB
Markdown
64 lines
2.5 KiB
Markdown
# Group uncommon
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Certain features of the FLAC format are non-subset or otherwise
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uncommonly used. Decoders might not be able to playback these
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files, but they should detect this inability and preferably
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notify the user rather than crash of freeze. Read the
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README.txt in the directory uncommon for details on each file.
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Note that despite the features being used are uncommon, these
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files are still valid FLAC files.
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## Manifest
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- File 01 has a sample rate that changes mid-stream. The file
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starts with a sample rate of 32kHz and switches to 24kHz,
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16kHz and finally 48kHz.
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- File 02 has a number of channels that increases mid-stream.
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The file starts with 1 channel, changes to stereo and ends
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with 6 channels.
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- File 03 has a number of channels decreases mid-stream. It
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starts with 4 channels, changes to stereo and ends with
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1 channel.
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- File 04 has a bit depth that changes mid-stream. It starts
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with a bit depth of 16, changes to 8 and ends with 24.
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- File 05 has a bit depth of 32 bit per sample.
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- File 06 has a sample rate of 768kHz. Because this sample
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rate cannot be described in the FLAC frame header, files
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with this sample rate are not streamable and not subset.
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- File 07 has a bit depth of 15 bit per sample. Because this
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bit depth cannot be described in the FLAC frame header,
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files with this bit depth are not streamable and not subset.
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- File 08 has a block size of 65535 samples, which is the
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largest possible block size in FLAC. File using such large
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blocks are not subset.
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- File 09 has one subframe with a rice partition order of 15,
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which is the highest possible partition order. In effect
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it means each partition in that subframe contains only a
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single sample. Such an extreme might trigger peculiar
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behaviour in a decoder.
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- File 10 is a FLAC file that starts directly at a frame
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header, which means the fLaC marker is absent and no
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metadata is present either. While this is not a recommended
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format to store audio data in, it simulates the way a FLAC
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stream is received when multicast. Additionally, the frame
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numbers of the frames in the stream are rather high which
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can happen when streaming uninterrupted for a long time.
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- File 11 is similar in purpose to file 10, but this file has
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unparsable data preceding the first FLAC frame header. This
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better simulates receiving a multicast FLAC stream, because
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the first received packet of a multicast stream might not
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align with a frame boundary, as a frame might be split over
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several packets.
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