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BitJazz SheerVideo FAQ Speed: Introduction
How fast is SheerVideo?
Is SheerVideo symmetrical in speed?
How fast is SheerVideo? On a mid-range personal computer such as a single-processor 1 GHz Mac G4, going from RAM to RAM,
SheerVideo encodes at about 115 MB/s (megabytes per second) or 110 MiB/s (mebibytes per second) for all supported formats,
and decodes at about 105 MB/s or (100 MiB/s) for all formats
except progressive-scan Y'CbCr 8bv/w 4:2:2p, which it decodes at about 90 MiB/s.
On a moderately fast personal computer such as a dual-processor 1.25 GHz Mac G4,
SheerVideo decodes 2.5 times as fast, 260 MB/s (250 MiB/s).
On a low-end personal computer such as a 1 GHz Mac G3, SheerVideo encodes and decodes
all supported interlaced formats at around 80 MiB/s,
and progressive-scanned formats at around 60 MiB/s.
On a faster machine, SheerVideo is correspondingly faster.
Note that with SheerVideo, unlike with other codecs,
the bottleneck is not the codec, but the input and output devices,
because SheerVideo runs substantially faster than just about any storage device or transmission channel.
In other words, for RAM-to-disk capture, disk-to-disk editing, or disk-to-VRAM playback
with SheerVideo to run at the RAM-to-RAM speeds reported here,
you have to have i/o devices to match.
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Is SheerVideo symmetrical in speed? Yes, SheerVideo is nearly symmetrical in speed.
On a G3 processor, SheerVideo typically decodes about 5% faster
than it encodes,
while on a G4 processor, encoding is typically about 10% faster than decoding.
Speed symmetry is important in production and interchange,
where encoding and decoding are both frequent and time-critical.
For archival, where content is always compressed and rarely decompressed,
it's okay for a codec to decompress slowly, as long as it compresses quickly.
For distribution, where content is compressed once and may be decompressed millions of times,
it's worth letting a codec take extra time to compress the data further,
and the decompressor generally doesn't need to be any faster than real-time.
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