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