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BitJazz
SheerVideo FAQ
Formats: Ancillary Channels
Does SheerVideo support alpha?
 Does SheerVideo support alpha?
Yes, SheerVideo supports real-time lossless encoding and decoding of an alpha compositing channel along with the color channels, for all
RGB[A] 10bf,
RGB[A] 8bf,
Y'CbCr[A] 10bv 4:4:4[:4],
Y'CbCr[A] 8bv 4:4:4[:4],
Y'CbCr[A] 8bu 4:4:4[:4],
Y'CbCr[A] 10bv 4:2:2[:4], and
Y'CbCr[A] 8bv 4:2:2[:4] pixel formats,
both progressive and interlaced, at all resolutions and frame rates, on both Mac and Windows.
You choose whether or not to encode alpha with a Sheer codec
by choosing the appropriate item in the Depth pop-up menu in the Compression Settings dialog:
- Millions of Colors: ignore alpha
- Millions of Colors+: store alpha
Note that the QuickTime Compression Settings dialog incorrectly says "Millions" of Colors,
instead of "Billions" (or "Milliards") of Colors for 10-bit color formats or "Quintillions" of Colors for 16-bit color formats,
even though QuickTime correctly supplies the full 10-bit or 16-bit precision required by the codec.
The optional alpha-channel support is indicated in the specific Sheer codec names by a bracketed 'A' ([A])
after the color-space name;
Sheer Y'CbCr codecs supporting an optional alpha channel also have an extra ':4' in brackets ([:4])
at the end of the sampling designation:
- Sheer RGB[A] 10bf
- Sheer RGB[A] 8bf
- Sheer Y'CbCr[A] 10bv 4:4:4[:4]
- Sheer Y'CbCr[A] 8bv 4:4:4[:4]
- Sheer Y'CbCr[A] 10bv 4:2:2[:4]
- Sheer Y'CbCr[A] 8bv 4:2:2[:4]
When alpha channel encoding is selected, the presence of the alpha channel is indicated by an unbracketed 'A'
after the color-space name in the format name;
Sheer Y'CbCrA format names also have an extra unbracketed ':4' at the end of the sampling designation:
- Sheer RGBA 10bf p
- Sheer RGBA 10bf i
- Sheer RGBA 8bf p
- Sheer RGBA 8bf i
- Sheer Y'CbCrA 10bv 4:4:4:4i
- Sheer Y'CbCrA 10bv 4:4:4:4p
- Sheer Y'CbCrA 8bv 4:4:4:4i
- Sheer Y'CbCrA 8bv 4:4:4:4p
- Sheer Y'CbCrA 8bu 4:4:4:4i
- Sheer Y'CbCrA 8bu 4:4:4:4p
- Sheer Y'CbCrA 10bv 4:2:2:4i
- Sheer Y'CbCrA 10bv 4:2:2:4p
- Sheer Y'CbCrA 8bv 4:2:2:4i
- Sheer Y'CbCrA 8bv 4:2:2:4p
Alpha represents the coverage or opacity of the pixel,
which is used during compositing.
When composited over a background image,
a transparent foreground pixel lets only the background show through,
while an opaque foreground pixel shows only the foreground,
and anything in between shows a mixture of foreground and background.
SheerVideo supports the alpha-containing RGBA 10+bf pixel formats
'b64a',
'L64A', and
'A46L';
the alpha-containing RGBA 8bf pixel formats
ARGB,
'ABGR',
'RGBA',
and 'BGRA';
the alpha-containing RGBA 8bv'VRGB',
the alpha-containing Y'CbCrA 8bv 4:4:4:4 pixel formats
'v408', and
'VUYA'.
the alpha-containing Y'CbCrA 10+bu 4:4:4:4 pixel format
'r4fl'.
and the alpha-containing Y'CbCrA 8bu 4:4:4:4 pixel format
'r408'.
QuickTime does not currently define any alpha-containing Y'CbCrA 10bv 4:4:4:4, Y'CbCrA 10bv 4:2:2:4, or Y'CbCrA 10bv 4:2:2:4 pixel formats.
The specific Sheer codec corresponding to alpha-containing RGBA 10bf pixel formats is
which encodes from and decodes to RGB[A] 10bf pixel formats losslessly in real time.
The Sheer RGB[A] 8bf codec also encodes from and decodes to RGB[A] 10bf formats in real time, but only to 8 bits of precision.
The Sheer Y'CbCr[A] 10bv 4:4:4[:4], Sheer Y'CbCr[A] 8bv 4:4:4[:4], Sheer Y'CbCr[A] 10bv 4:2:2[:4], and Sheer Y'CbCr[A] 8bv 4:2:2[:4] codecs
also encode from and decode to RGB[A] 10bf formats, but not losslessly, and not always in real time.
The generic Sheer codec encodes RGB[A] 10bf pixel formats as Sheer RGB[A] 10bf.
The specific Sheer codec corresponding to alpha-containing RGBA 8bf pixel formats is
which encodes from and decodes to RGB[A] 8bf pixel formats losslessly in real time.
The Sheer RGB[A] 10bf codec also encodes from and decodes to RGB[A] 10bf pixel formats losslessly in real time.
The Sheer Y'CbCr[A] 10bv 4:4:4[:4] codec also encodes from and decodes to RGB[A] 8bf pixel formats losslessly using Synchromy, though not always in real time.
The Sheer Y'CbCr[A] 8bv 4:4:4[:4], Sheer Y'CbCr[A] 10bv 4:2:2[:4], and Sheer Y'CbCr[A] 8bv 4:2:2[:4] codecs also encode from and decode to RGB[A] 8bf formats,
though not losslessly and not always in real time.
The generic Sheer codec encodes RGB[A] 8bf pixel formats as Sheer RGB[A] 8bf.
The specific Sheer codec corresponding to alpha-containing Y'CbCrA 10bv 4:4:4:4 pixel formats is
- Sheer Y'CbCr[A] 10bv 4:4:4[:4]
which encodes from and decodes to Y'CbCr[A] 10bv 4:4:4[:4] pixel formats losslessly in real time.
The Sheer Y'CbCr[A] 8bv 4:4:4[:4] codec also encodes from and decodes to Y'CbCr[A] 10bv 4:4:4[:4] pixel formats in real time, but only to 8 bits of precision.
The Sheer RGB[A] 10bf, Sheer RGB[A] 8bf, Sheer Y'CbCr[A] 10bv 4:2:2[:4], and Sheer Y'CbCr[A] 8bv 4:2:2[:4] codecs
also encode from and decode to Y'CbCr[A] 10bv 4:4:4[:4], but not losslessly, and not always in real time.
The generic Sheer codec encodes Y'CbCr[A] 10bv 4:4:4[:4] pixel formats as Sheer Y'CbCr[A] 10bv 4:4:4[:4].
The specific Sheer codec corresponding to alpha-containing Y'CbCrA 8bv 4:4:4:4 pixel formats is
- Sheer Y'CbCr[A] 8bv 4:4:4[:4]
which encodes from and decodes to Y'CbCr[A] 10bv 4:4:4[:4] pixel formats losslessly in real time.
The Sheer Y'CbCr[A] 10bv 4:4:4[:4] codec also encodes from and decodes to Y'CbCr[A] 8bv 4:4:4[:4] pixel formats losslessly in real time.
The Sheer RGB[A] 10bf codec also encodes from and decodes back to Y'CbCr[A] 8bv 4:4:4[:4] pixel formats losslessly (except for out-of-range colors) using Synchromy,
though not always in real time.
The Sheer RGB[A] 8bf, Sheer Y'CbCr[A] 10bv 4:2:2[:4], and Sheer Y'CbCr[A] 8bv 4:2:2[:4] codecs also encode from and decode to Y'CbCr[A] 8bv 4:4:4[:4] formats,
though not losslessly and not always in real time.
The generic Sheer codec encodes Y'CbCr[A] 8bv 4:4:4[:4] pixel formats as Sheer Y'CbCr[A] 8bv 4:4:4[:4].
The specific Sheer codec corresponding to alpha-containing Y'CbCrA 8bu 4:4:4:4 pixel formats is
- Sheer Y'CbCr[A] 8bu 4:4:4[:4]
an unbiassed variant of the Sheer Y'CbCr[A] 8bv 4:4:4[:4] codec,
which encodes from and decodes to Y'CbCr[A] 8bu 4:4:4[:4] pixel formats losslessly in real time.
The Sheer Y'CbCr[A] 10bv 4:4:4[:4] codec also encodes from and decodes to this format losslessly (except for out-of-range colors) in real time.
The Sheer RGB[A] 10bf codec also encodes from and decodes to Y'CbCr[A] 8bu 4:4:4[:4] pixel formats losslessly (except for out-of-range colors) using Synchromy, but not always in real time.
The Sheer RGB[A] 8bf, Sheer Y'CbCr[A] 10bv 4:2:2[:4], and Sheer Y'CbCr[A] 8bv 4:2:2[:4] codecs also encode from and decode to Y'CbCr[A] 8bu 4:4:4[:4], but not losslessly and not always in real time.
The generic Sheer codec and the Sheer Y'CbCr[A] 8bv 4:4:4[:4] codec encode Y'CbCr[A] 8bu 4:4:4[:4] pixel formats as Sheer Y'CbCr[A] 8bu 4:4:4[:4].
The specific Sheer codec corresponding to alpha-containing Y'CbCr[A] 10bv 4:2:2[:4] pixel formats is
- Sheer Y'CbCr[A] 10bv 4:2:2[:4]
which encodes from and decodes to Y'CbCr[A] 10bv 4:4:4[:4] pixel formats losslessly in real time.
The Sheer Y'CbCr[A] 8bv 4:2:2[:4] codec also encodes from and decodes to Y'CbCr[A] 10bv 4:2:2[:4] formats in real time, but only to 8 bits of precision.
The Sheer RGB[A] 10bf, Sheer RGB[A] 8bf, Sheer Y'CbCr[A] 10bv 4:4:4[:4], and Sheer Y'CbCr[A] 8bv 4:4:4[:4] codecs also encode from and decode to Y'CbCr[A] 10bv 4:2:2[:4] formats,
though not losslessly and not always in real time.
The generic Sheer codec encodes Y'CbCr[A] 10bv 4:2:2[:4] pixel formats as Sheer Y'CbCr[A] 10bv 4:2:2[:4].
The specific Sheer codec corresponding to alpha-containing Y'CbCr[A] 8bv 4:2:2[:4] pixel formats is
- Sheer Y'CbCr[A] 8bv 4:2:2[:4]
which encodes from and decodes to Y'CbCr[A] 10bv 4:4:4[:4] pixel formats losslessly in real time.
The Sheer Y'CbCr[A] 10bv 4:2:2[:4] codec also encodes Y'CbCr[A] 8bv 4:2:2[:4] pixel formats losslessly in real time.
The Sheer RGB[A] 10bf, Sheer RGB[A] 8bf, Sheer Y'CbCr[A] 10bv 4:4:4[:4], and Sheer Y'CbCr[A] 8bv 4:4:4[:4] codecs also encode from and decode to Y'CbCr[A] 8bv 4:2:2[:4],
though not losslessly and not always in real time.
The generic Sheer codec encodes Y'CbCr[A] 8bv 4:2:2[:4] pixel formats as Sheer Y'CbCr[A] 8bv 4:2:2[:4].
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