mxf files and their issues with playing stereo audio

digilyd wrote on 11/19/2017, 7:12 AM

I discovered that when I encode as best quality .mxf file for upload to youtube specifically to avoid multiple stages of perceptual encoding I get mono audio on youtube. It also appears that VLC allows only playback of one track or the other but not both. Why the (insert preferred expletive here) do whomever conceived that folly think a stereo recording of the sound is made in the first place?

Is there a workaround or remedy for this apparently idiotic current sitaution?

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Comments

Former user wrote on 11/19/2017, 7:59 AM

You will need to be more specific on your render settings. MXF is just a wrapper that can contain any number of codecs and audio formats. Please state which codecs you are usiing or at least which template you are using to render. That will make it easier to give you advice.

rraud wrote on 11/19/2017, 8:41 AM

Most of the forum members here (many of which are expert level) encode an AVC/AAC file (.mp4) for YT or Vim. I'm not a video expert, but I've never had any YT issues uploading AAC audio.

NickHope wrote on 11/19/2017, 8:59 AM

Supported YouTube file formats

No mention of MXF there. I stick to AVC (x264, crf-16-18) with high-bitrate AAC in an MP4 wrapper. This thread is worth a look: https://www.vegascreativesoftware.info/us/forum/faq-how-can-i-improve-the-quality-of-my-avc-h-264-renders--104642/

Also, I suggest doing this to make YouTube serve your video as VP9 instead of AVC.

digilyd wrote on 11/19/2017, 11:15 AM

This is the format chosen:

Audio: 48.000 Hz; 16 Bit; Stereo; PCM
Video: 25 fps; 1920x1080 Upper field first; MPEG HD
Pixel Aspect Ratio: 1,000

Video bit rate is specified as "35 (VBR) HQ"

It is not ambiguous and I went for it partly because it is my archive format anyway and partly because my soundcloud experience is that full wordlenght audio is the optimal choice. I have seen it mentioned that youtube will reencode everything and it is known and described if not in the literature then as good radio station practice that serial perceptual audio encoding should be avoided, no matter the bitrate. Youtube has not refused it and not warned that it would use one stereo channel, left assumed, and just discard the other because that there newfangled stereo is probably not going to last anyway.

Since it is specified as stereo I tend to assume that it should be reproduced as stereo. I learned about this format and its virtue of full wordlength audio because I got video in it from a borrowed Sony camera that can record in it. Considering the high video bitrate it is an absurd concept that there should not be enough bandwidth to read both audiotracks. So to me, ignorant as I am of these things, it looks like a systemic failure, when not only youtube but also VLC has a problem, then perhaps there is more to it than just a youtube setup oddity. Consequently I asked a support question there, but I am not overenthusiastically believing that it will get to second or third level support.

I just tried an AVC testrender, but - much like the difference between raw formats and jpg on a still camera - it is bleakier and slightly foggy with less full colours. That I can live with, but I want my audio to be as good as I record it using separate high quality equipment. Multiple stages of perceptual encoding is not good for naturally recorded violins.

I checked a couple of mp4's from them, one - uploaded as mpeg2 - has a stereo bitrate of 96 kbit/s and the other, the one I detected the problem with today a mono bitrate of 144 kbit/s.

A well, it is probably as hopeless as when youtubes robot comes up with a copyright claim on an arrangement for solo flute of a work for solo flute from 1720, so I'll just try to implement all suggestions, thanks guys!

- Peter Larsen

NickHope wrote on 11/19/2017, 8:06 PM

...Video: 25 fps; 1920x1080 Upper field first; MPEG HD...

If it's really interlaced footage with movement, it would be a good idea to deinterlace that before upload. Section 5 of that same link has info on that. If you don't, then YouTube either won't deinterlace it, so you may see combing, or they'll not make a high quality job of deinterlacing it.

digilyd wrote on 11/22/2017, 1:57 AM

It invariably is footage with movement, I didn't worry about that - partly because I know well where my huge field of ignorance is :) - and just, to the best of my knowledge - stayed in the format from the camera. AVC is then the solution, albeit not a good one because of the audio deterioration caused by multiple stages of perceptual coding, but the least bad one, the Devils Choice. I didn't worry about upload time because there is no additional use of mains power when the dual xeon is rendering anyway and did note that the parameter for choosing AVC appeared to be just that, upload time. Thank you once again for all comments :)

- Peter Larsen