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Bit Rate is too low when exporting from Premiere to MXF / OP1a
Hello,
I am trying to follow a spec sheet for a broadcast delivery to export a file from Premiere CC 12.0.1 – the broadcaster wants Op1a, 25 fps interlaced, minimum data rate 50 Mbps.
I have not made this kind of file before, but did some reading/ googling and everything has seemed relatively straightforward. I am using the MXF OP1a XDCAM HD 50 PAL 50i preset and only adjusting the number of audio tracks (broadcaster wants 8 channels), otherwise using it as is.
My understanding is that the data rate with this preset should be 50 Mbps… correct?
But after I export the file and open it in Quicktime inspector to make sure all the specs are correct, it is showing me that the data rate is 9.22 MBps. I have done this export over and over again and the number is always the same. But there seems to be no way to adjust the data rate for the export—everything I have read says that you just pick the format and the right data rate should be automatic.
I don’t want my file to be rejected for a data rate that is too low… not sure what is causing this and I don’t see anywhere to adjust a setting to fix it. Help?
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16 Replies
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Well, I know that my XDCAM 422 29.97 exports will have a data rate of 50mbps. And that with 25fps, the data rate will be lower, due to less FPS. But I don’t think THAT much lower.
Shane
Little Frog Post
Read my blog, Little Frog in High Def -
Isn’t the whole point of the XDCAM 50 preset that it is supposed to ensure a data rate of 50? There seems to be no place to adjust this parameter, so I have not idea how to generate the right kind of file other than selecting the preset called 50.
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How would I set that up? In the MXF OP1a export menu I can either choose to match to my sequence settings (which gives me an error message / doesn’t work), or I need to select a format. I selected XDCAM 50 PAL 50i, and with this selected there is no way to manually change the bit rate. Is there some other way to customize my export that I am not seeing that would allow me to change it? Could you give more detail about what you are recommending?
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Quicktime is probably showing the information wrong and it is also a really bad tool for making any kinds of serious checks. The bit rate is specced in the format and should be fine. Also even though it is 50 Mbps CBR it’s still being compressed by what is happening in the footage. If you have simple footage, long takes, full screen graphics, crop bars etc those are easier to compress and will take less space. If I remember correctly only only MPEG IMX will write every frame with all the data in it. Which is kinda wasteful.
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ok, thank you! This is the first response that makes sense to me. Actually, yes, the film has a lot of long takes and quote static shots, so what you are saying seems very plausible.
Can you recommend a different inspector that I can use to get more accurate information about the file other than QT inspector?
The file actually looks fine to me—if I play it side by side with the higher data rate ProRes file it doesn’t look really different to my eye, but I’m concerned that the broadcaster will see that the data rate number looks too low and will reject it.
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[renee litapop] “ut I’m concerned that the broadcaster will see that the data rate number looks too low and will reject it.”
XDCAM HD 422 is a locked down specification. There are no settings to set. It will be to format specs. There can be other issues that aren’t format related like out of gamut colors, wrong audio levels etc. I’ve delivered hundreds if not a thousand files in this spec and none of them have had any issues with bit rate. If they have an automated QC-check they will let you know if/what you need to fix.
QC is a very specialized field with really expensive solutions but there are some free ones like MediaArea’s QCtools.
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You opened one of these MXF files in QuickTime? When I do that QT converts the file – I assume to h264. Did that happen when you opened it? If that’s the case, you are not actually looking at the mxf file. Open the file in VLC and check the Media Information. VLC can open the mxf. And there you should be able to find the Media Bitrate.
TC -
Will the broadcaster accept DNx? We regularly export DNxHR/DNxHD MXF OP1a out of Premiere for masters. You’ll have no problem getting a minimum data rate 50 Mbps with DNx.
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I saw that there was a whole other DNx export menu, and I am not sure what the difference is. The specs provided seemed to exactly match the setting I used (MXF XDCAM 50i). Is DNx a different wrapper? Can you explain the difference between those two export menus?
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DNxHD/HR are completely different formats from what you’ve been asked. You should deliver to a format that they have in their delivery specification.
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