output
-Swscale has 2 scaler paths, each side must be capable to handle
-slices, that is consecutive non overlapping rectangles of dimension
+Swscale has 2 scaler paths. Each side must be capable of handling
+slices, that is, consecutive non-overlapping rectangles of dimension
(0,slice_top) - (picture_width, slice_bottom)
special converter
- This generally are unscaled converters of common
+ These generally are unscaled converters of common
formats, like YUV 4:2:0/4:2:2 -> RGB15/16/24/32. Though it could also
in principle contain scalers optimized for specific common cases.
Main path
- The main path is used when no special converter can be used, the code
- is designed as a destination line pull architecture. That is for each
+ The main path is used when no special converter can be used. The code
+ is designed as a destination line pull architecture. That is, for each
output line the vertical scaler pulls lines from a ring buffer. When
the ring buffer does not contain the wanted line then it is pulled from
the input slice through the input converter and horizontal scaler, and
Input to YUV Converter
When the input to the main path is not planar 8bit per component yuv or
- 8bit gray then it is converted to planar 8bit YUV, 2 sets of converters
- exist for this currently one performing horizontal downscaling by 2
+ 8bit gray then it is converted to planar 8bit YUV. 2 sets of converters
+ exist for this currently, one performing horizontal downscaling by 2
before the conversion and the other leaving the full chroma resolution
but being slightly slower. The scaler will try to preserve full chroma
- here when the output uses it, its possible to force full chroma with
- SWS_FULL_CHR_H_INP though even for cases where the scaler thinks its
+ here when the output uses it. It is possible to force full chroma with
+ SWS_FULL_CHR_H_INP though even for cases where the scaler thinks it is
useless.
Horizontal scaler
- There are several horizontal scalers, a special case worth mentioning is
+ There are several horizontal scalers. A special case worth mentioning is
the fast bilinear scaler that is made of runtime generated MMX2 code
using specially tuned pshufw instructions.
- The remaining scalers are specially tuned for various filter lengths
- they scale 8bit unsigned planar data to 16bit signed planar data.
+ The remaining scalers are specially tuned for various filter lengths.
+ They scale 8bit unsigned planar data to 16bit signed planar data.
Future >8bit per component inputs will need to add a new scaler here
that preserves the input precision.