On 6/1/2017 6:37 PM, Michael Niedermayer wrote: > On Tue, May 30, 2017 at 01:34:29PM -0400, Kevin Mark wrote: >> Variables pertaining to the main video are now available when >> using the scale2ref filter. This allows, as an example, scaling a >> video with another as a reference point while maintaining the >> original aspect ratio of the primary/non-reference video. >> >> Consider the following graph: scale2ref=iw/6:-1 [main][ref] >> This will scale [main] to 1/6 the width of [ref] while maintaining >> the aspect ratio. This works well when the AR of [ref] is equal to >> the AR of [main] only. What the above filter really does is >> maintain the AR of [ref] when scaling [main]. So in all non-same-AR >> situations [main] will appear stretched or compressed to conform to >> the same AR of the reference video. Without doing this calculation >> externally there is no way to scale in reference to another input >> while maintaining AR in libavfilter. >> >> To make this possible, we introduce eight new constants to be used >> in the w and h expressions only in the scale2ref filter: >> >> * main_w/main_h: width/height of the main input video >> * main_a: aspect ratio of the main input video >> * main_sar: sample aspect ratio of the main input video >> * main_dar: display aspect ratio of the main input video >> * main_hsub/main_vsub: horiz/vert chroma subsample vals of main >> * mdar: a shorthand alias of main_dar >> >> Of course, not all of these constants are needed for maintaining the >> AR, but adding additional constants in line of what is available for >> in/out allows for other scaling possibilities I have not imagined. >> >> So to now scale a video to 1/6 the size of another video using the >> width and maintaining its own aspect ratio you can do this: >> >> scale2ref=iw/6:ow/mdar [main][ref] >> >> This is ideal for picture-in-picture configurations where you could >> have a square or 4:3 video overlaid on a corner of a larger 16:9 >> feed all while keeping the scaled video in the corner at its correct >> aspect ratio and always the same size relative to the larger video. >> >> I've tried to re-use as much code as possible. I could not find a way >> to avoid duplication of the var_names array. It must now be kept in >> sync with the other (the normal one and the scale2ref one) for >> everything to work which does not seem ideal. For every new variable >> introduced/removed into/from the normal scale filter one must be >> added/removed to/from the scale2ref version. Suggestions on how to >> avoid var_names duplication are welcome. >> >> var_values has been increased to always be large enough for the >> additional scale2ref variables. I do not forsee this being a problem >> as the names variable will always be the correct size. From my >> understanding of av_expr_parse_and_eval it will stop processing >> variables when it runs out of names even though there may be >> additional (potentially uninitialized) entries in the values array. >> The ideal solution here would be using a variable-length array but >> that is unsupported in C90. >> >> This patch does not remove any functionality and is strictly a >> feature patch. There are no API changes. Behavior does not change for >> any previously valid inputs. >> >> The applicable documentation has also been updated. >> >> Signed-off-by: Kevin Mark <kmark...@gmail.com> >> --- >> doc/filters.texi | 26 ++++++++++++++++++- >> libavfilter/scale.c | 72 >> ++++++++++++++++++++++++++++++++++++++++++++++++++--- >> 2 files changed, 93 insertions(+), 5 deletions(-) > > applied > > can you add a fate test that uses the new identifers ? > > Thanks
This broke 820 tests with Valgrind. All of them seem to point to ==1253== Invalid read of size 8 ==1253== at 0x697ECA: ff_scale_eval_dimensions (scale.c:118) _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
