[FFmpeg-devel] [PATCH 3/8] avcodec/jpeglsenc: Move check out of loop

Paul B Mahol onemda at gmail.com
Sun Sep 6 20:02:51 EEST 2020

On Sat, Sep 05, 2020 at 01:17:11AM +0200, Andreas Rheinhardt wrote:
> ls_encode_line() encodes a line of input, going from left to right. In
> order to calculate a predicted value it uses the left and upper-left
> value of the output picture (that is, it uses how a decoder would see
> the already encoded part of the picture), unless this is the very first
> pixel of this line in which case one uses the first pixel of the last
> (upper) line and the line before the last line. Therefore the loop
> contained a check for whether this is the beginning of a new line. This
> commit moves said check out of the loop by initializing these values
> before the loop and by updating these values at the end of the loop
> body; already read/calculated values are reused for this (the prediction
> also needs the value of the upper pixel and this can be reused for the
> upper left value of the next iteration of the loop).
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>  libavcodec/jpeglsenc.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)

probably ok

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