Am 05.05.2015 um 09:06 schrieb tim nicholson:
On 02/05/15 14:38, Christoph Gerstbauer wrote:
Am 01.05.15 um 11:21 schrieb tim nicholson:
[..]
Christoph do you actually require the mxf metadata setting (as it really
ought to be, and what I thought you were after) or are you content with
it in the essence, in which case, in the absence of a target preset, you
will have to set the flags yourself.
As Marton Balint showed me the syntax, the setting of these 4 values
worked, but they dont affect the metadata in the MXF container.
The metadata flags:
Color Siting and Signal Standard werent changed by using the syntax.
Before this test I though I could change these 2 params with the syntax
descriped above.
But now I know that this is not working.
Furthermore I looked for a way to PASS the test with the IRT Analyzer.
Regarding to the ticket: "How to set 3 specific metadata flags
(ITU601/displayoffset) in FFmpegs IMX50 MXF-OP1a encoding"
Yes I am still looking for a encoding option fot the mxf encoding of
ffmpeg to set MANUALLY (of course) the flags for Signal Standard and
Color Siting.
FFmpeg should never set it autmatically to any values, if the source
would have empty flags.
So if I know from which source the content is comming, I want to be able
to set the 2 mxf metadata flags, and also the 4 addional falg for the
essence (color_range, color_space, color_transfer and color_primaries).
Setting the values to a specified values seems straightforward enough,
now I have found the relevant UL's.
The tricky bit is to decide what to do if the values aren't manually
specified. According to the specs there is no "default" value, so we
would have to "invent" one.
Hm, so what is happening at the current ffmpeg encoding? If nothing is
defined what is going into the 2 mxf metadata flags?
At this time the following is readed out from mxf2raw:
Signal Standard = 0 (NONE)
Color Sitting = 255 (UNKNOWN)
So is ffmpeg writing this "0" into the mxf or is MXF2RAW showing me the
some standard value when it cannot regognize any value in this flags?
This could be by inspecting the codec
metadata to see if the corresponding stream flags are set. This looks
like it would be tricksy, or using some predetermined value based upon
some other parameters such as frame size, which could lead to
disagreement as to what was appropriate.
Making the writing of the metadata optional also adds complication in
the muxer, so it needs some careful thought.
As an interim solution for pristine mxf files, have you tired remuxing
with bmxlib?
Never tried this way :) I just used mxf2raw to check the files.
But I will try this way too. Thank you for the hint.
Best Regards
Christoph
My motivation to this whole issue is:
I want to generate a IMX50 file from an ffv or ffvhuff file were the
IMX50 target file has less transcoding loss as possible.
Most transcoders I use make an internal convertion from YUV422 to YUV422
formats (e.g uncompress 4:2:2 to uncompressed 4:2:2) with an ADDIONAL
loss. I guess it is an internal RGB convertion: YUV422 source to RGB
(internal) to YUV422 target format. (anyway, these transcoders are black
boxes and I cannot know if this is the cause)
So when I transcode with these transcoders I have 2 LOSSY steps:
1.) Avoidable LOSS of source is YUV422: addional chroma subsampling
(RGB->YUV422)
2.) MPEG2 encoding loss
FFmpeg does not do that: It keeps the yuv422 native format and just
encode it to mpeg2. -> And that would lead to better quality IMX files.
Therefore I want to switch from "professional" transcoders to ffmpeg for
generation IMX50. But I will still ned this metadata flag to do it
perfectly.
Best Regards
Christoph Gerstbauer
Regards,
Marton
[..]
_______________________________________________
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-user
_______________________________________________
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-user
