Thank you very much for confirming at least a part of my mental model ;)
Followup questions inlined below:
On 05/09/2016 10:29 AM, Paul B Mahol wrote:
On 5/6/16, Peter Rabbitson <[email protected]> wrote:
...
== Questions
- What is the "default" conversion matrix used within ffmpeg when
nothing else is specified. Is it (apparently) bt.601, or does it default
to different things depending on input?
You are using color source filter which is using fixed coeff (bt.601) when
converting color from rgb to yuv. There is nothing much you can do about
this.
Is this documented somewhere?
My actual use case btw is 24bit rgb via image2pipe as in:
> ... -f image2pipe -c:v ppm -i /dev/stdin ...
which behaves the same way as the internal color source I used in the
example.
- If it is bt.601 is it bt470bg or is it smpte170m or in the matrix case
it doesn't matter?
I think this question got skipped in the answer.
- Is it "ok" to produce 720p video explicitly tagged at bt.601? I ran
across multiple writeups on the net suggesting 720p not encoded (is this
the right term?) in bt.709 is a big no-no.
It is "ok" to produce it, but not all encoders support proper tagging right
colorspace in their bitstream... so better be safe than sorry and not
produce such files.
- Regardless of what the answer to the previous question is: If I wanted
to produce the same example video in bt.709 and have it play correctly
in both cases - what would the ffmpeg incantation be?
FFmpeg doesn't play videos, it decodes them. FFplay is more a tool
for testing than proper playback.
I phrased this last question incorrectly. Given my source *is* rgb, and
I want to produce a final 1280x720 yuv444p h264 bitsream, to be consumed
by whatever player (both hardware and softwre):
What is the correct ffmpeg *encoding* incantation?
- Am I correct that the inconsistency #00AA00 => #00AB01 is simply "cost
of doing YUV business", or is the reason more nuanced/involved?
This question also got skipped, and I am really keen on understanding
whether colors can in fact roundtrip, or there is a limit due to the
very physics the different colorspaces model. I see there is a large
array of knobs to twiddle in `man ffmpeg-scaler` related to chroma but
there is sadly no layman-friendly entry-point.
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