This reverts commit dea673d0d5.
This change cannot work for several reasons, the most obvious ones are:
- the alpha is being part of the scoring of the color difference, even
though we can not interpret the alpha as part of the perception of the
color (we don't even know if it's premultiplied or postmultiplied)
- the colors are averaged with their alpha value which simply cannot
work
The command proposed in the original thread of the patch actually
produces a completely broken file:
ffmpeg -y -loglevel verbose -i fate-suite/apng/o_sample.png -filter_complex "split[split1][split2];[split1]palettegen=max_colors=254:use_alpha=1[pal1];[split2][pal1]paletteuse=use_alpha=1" -frames:v 1 out.png
We can see that many color pixels are off, but more importantly some
colors have a random alpha value: https://imgur.com/eFQ2UK7
I don't see any easy fix for this unfortunately, the approach appears to
be flawed by design.
New option can be used to avoid creating very short segments with inputs
whose GOP size is variable or unharmonic with segment_time.
Only effective with segment_time.
We shouldn't be providing links to unverified and non-FFmpeg-controlled
content in our documentation.
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
We do not endorse or recommend specific third party servers or companies
that users' data will be funneled through.
It is also incorrectly describing how FFmpeg currently works.
Should have been part of 412922cc6f but was
missed.
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Bring it up to date with current practice, as the current text does not
cover everything. Drop the reference to unprefixed exported symbols,
which do not exist anymore.
It describes a general development policy, not code formatting. It is
also not true, as these days we tend to prioritize correctness, safety,
and completeness over code size.
It is currently very out of touch with reality.
* declare we are using C99 fully, rather than C90 plus extensions
* mention our use of stdatomic.h
* mention forbidden C99 features, like VLAs and complex numbers
VP6 alpha in EA format is a second VP6 encoded video stream where only the Y
component is used and is interpreted as the alpha channel of the first VP6
stream. The alpha VP6 stream is muxed separately from the main VP6 stream, has
its own stream headers and packet headers. In theory the two streams might not
even have the same resolution (although most likely that is not something that
is seen or supported in the wild), but the format is capable of doing it.
Merged VP6 alpha (also known as the VP6A codec) means that a packet of the
video stream contains the corresponding packet of both VP6 substreams like
this:
{OffsetOfAlpha, DataPacket, AlphaDataPacket}
So data and alpha data of a frame is merged to a single packet, this is how VP6
video with alpha is muxed in FLV and SWF.
The first approach is more like how the demuxer sees data in the EA format,
unfortunately it is different to what the FLV or SWF format expects, so -
having no better place for it in the framework - I decided to do an optional
format conversion in the EA demuxer.
Signed-off-by: Marton Balint <cus@passwd.hu>
Add qsv_transcode example which shows how to use qsv to do hardware
accelerated transcoding, also show how to dynamically set encoding
parameters.
examples:
Normal usage:
qsv_transcode input.mp4 h264_qsv output.mp4 "g 60"
Dynamic setting usage:
qsv_transcode input.mp4 hevc_qsv output.mp4 "g 60 asyne_depth 1"
100 "g 120"
This command initializes codec with gop_size 60 and change it to
120 after 100 frames
Signed-off-by: Wenbin Chen <wenbin.chen@intel.com>
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>
As a result of a typo in the source code, this option was completely
non-functional. In order to fix it, without breaking the current default
behavior, explicitly change this default to 0.
This behavior is also consistent with how other scale filters behave by
default, so it's probably best to enshrine it anyways.
Drop the reference to directly committing code, because
- it is highly discouraged and very rarely done these days
- there is no good reason NOT to submit patches for review
Add a link to the development policy chapter.
