[FFmpeg-devel] [PATCH] vf_scale: Detecting changes of incoming frame properties and dinamically evaluate width and height expressions

Paul B Mahol onemda at gmail.com
Wed Jan 20 10:05:49 CET 2016

On 1/19/16, Bodecs Bela <bodecsb at vivanet.hu> wrote:
> Hi All,
> currently scale video  filter accepts expressions in its width and height
> parameters but evaluates them only once at init and replaces them with
> their actual values. Later on, if any parameter of incoming frames
> changes - ie those were used in the original size expressions - then
> they new values will not have any affect for width and heigth values.
> They remain the same. This patch makes possible that width and height
> expressions be evaluated frame-by-frame basis if width/height/sar/format
> properties of incoming frame would change. To retain the current
> behaviour and not to break any earlier app, a new config parameter has
> been introduced. Its name is "eval" and it has two distinct values:
> "init" and "frame". The default value is "init".
> This feature is very usefull in case of DVBT mpeg-ts streams where SAR
> may change
> time-by-time from 4/3 to 16/9 and vica-versa and the size remains the
> same and
> and you want to create a variable sized output with 1/1 SAR.
> Please consider to put this patch into the official ffmpeg source tree.
> thank you,
> Bela Bodecs

probably ok

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