[FFmpeg-user] FFMPEG's MXF container support for DNxHR with Avid MC?

[Alan Moore]

Hi Erik,

Thanks for you reply. I'm sorry for my late response but a surgery has kept
me away from this task for some time. Responses inline below.

On Sat, Dec 9, 2017 at 12:56 AM, Erik Dobberkau <erik.dobberkau at gmail.com>
wrote:

> Hi Alan,
>
> What should I expect in terms of being able to record or playback DNxHR in
> > MXF containers using FFMPEG and the compatibility of those clips in major
> > NLEs?
> >
>
> My personal take: Don't rely on anything. If you absolutely require using
> Avid MC,
> and there are major contraints, let MC do the conversion, and if something
> is wrong,
> you need to discuss this with Avid. It's nice there are tools out there
> like ffmpeg,
> or mxflib, or bmxlib, but in the end, when a vendor decides to do their own
> thing
> (see ProRes), I think it's "wrong" to expect open source projects to
> address this.
> There's always the option of hiring a knowledgeable developer to modify the
> current
> solution to fit your requirements.
>
>
Indeed. I've found MC to be especially picky about the files it will accept.


>
> > I see some support in FFMPEG source code (version 3.4) for DNxHR profiles
> > in libavcodec but the libavformat MXF read/write code doesn't seem to
> have
> > support for the new HR VCIDs (1270 - 1274), essence elements and other
> MXF
> > container meta data for DNxHR and yet... FFMPEG can read it's own MXF
> files
> > created with the DNxHR encoder. I'm guessing the MXF parser can read the
> > files by using the VCID in the *frame* header and ignores the VCID in the
> > MXF meta data/keys...
> >
>
> I'm expecting somebody will say "patch welcome" very soon... ;-)
>

Lolz, well, there may be some coming :-O


>
>
> > However, more importantly, the files do not "link" into Avid Media
> Composer
> > (using the MXF AMA plugin.) Is this known to work for anyone else? I'm
> > using MC version 8.8.1 (MacOS Sierra) and when I attempt to link the file
> > there is an error message saying it cannot link but no console log entry
> > saying exactly what it doesn't parse/like about the file.
> >
>
> It's been a while since I last checked, and I'm pretty certain I only did
> that with
> DNxHD, not DNxHR. Have you tried with DNxHD and had the same effect?
>
>
Yes, DNxHD links and works just fine. I'm not sure if DNxHR isn't working
because of how my code is calling the FFMPEG API (it's different than DNxHR
for performance reasons) or if it is something else. TBD.


>
> > I just need to know what works and what doesn't.
> >
>
> Some things do, some don't. In general the MXF wrapper is more a blessing
> than a curse because it imposes many contraints on a file when being
> written.
> But this also means not only to write correctly encoded pixel data, but
> also
> signaling the encoding parameters in the bitstream and the header
> correctly,
> which is where many tools fail. All in all, your mileage will vary here.
>

The MXF header/metadata seems to be the major sticking point with MC. The
frames (header & pixel data) are known to be correct.

On a separate note, is this the right place to ask questions about the
FFMPEG API or internals? The ffmpeg-dev list seems to be just patches...

Thanks for your input. I'll probably be back with more questions.


>
> Best,
> Erik
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