VideoHelp Forum

Our website is made possible by displaying online advertisements to our visitors. Consider supporting us by disable your adblocker or try DVDFab DRM and remove iTunes movie & music protection! :)
+ Reply to Thread
Results 1 to 3 of 3
  1. Hi.

    I am working on a semi-small production. My job is to receive a video from a picture editor. I then work the audio editing via Pro Tools (dialogue edit, sound design, and final mix). I bounce my file out of Pro Tools and deliver that.

    It turns out that the next person in the pipeline converts the technical specs of the video. I just saw the conversion specs, and was wondering if this sounds odd to everyone else. They convert the audio from 48k to 44.1k. I've never heard of anyone intentionally setting video audio to 44.1k before. Is that normal for a final version? They are also converting from 24fps to 29.98fps. That doesn't surprise me too much, but the 44.1k does.

    I don't know where they intend to air (or stream) the video. And I don't know what program they're using to convert the file.

    Also, on a side note (but kind of a big one), this is the 4th video I made for them. It turns out that they converted numbers 1 and 2 just fine. But they say that videos 3 and 4 had a black-screen after the conversion process. The audio worked fine, but the video was black. Does anyone know what might cause this? To me, it sounds like it might be a codec issue. But I really don't know where else to look. I'd like to be sure that the problem is not on my end. Since my final outputs play just fine on everyone's computer (including the people who are doing the conversions), it sounds like it's a problem on their end. But could it be possible that Pro Tools on my end is throwing a phantom-wrench into the system somewhere, which is then causing a black-screen on their end after conversion?

    I'm hoping someone else has come across this and figured it out.

    Quote Quote  
  2. Converting the audio from 48k to 44.1k seems pointless. 44.1k is pretty much just a CD thing these days, and from memory that was because Sony was involved in creating the CD spec and they already had a digital format that used a 44.1k sampling rate, and it worked well back in the analog days when video equipment was used to record digital audio.,100_Hz
    DVD and Bluray only officially support 48k. What's the final audio codec or target format?

    I've no idea on the black screen problem, but it does sound like a decoding issue.
    Quote Quote  
  3. Member Cornucopia's Avatar
    Join Date
    Oct 2001
    Deep in the Heart of Texas
    Search PM
    Not just pointless, but stupid and unprofessional.

    44.1 paradigm is proper for audio-centric recordings. 48 is THE standard for professional audio-for-video (and cinema). This goes for whole multiple sample rates also (88.2, 96, 176.4, 192). Anybody who is a pro should know that backwards and forwards. And you can tell them that I said so. DVD, Bluray, Broadcast, streaming, DCI, it doesn't matter - 48! Suggesting otherwise is sloppy and/or arrogantly ignorant.

    As far as the black frame, you should be conferring with your video editor, but MOST pro productions shoot VIDEO @ 25/50fps if in PAL areas, or VIDEO @ 29.97/59.94fps if in NTSC areas, or 24 if specifically for film/DCI cinema. But since most editing apps expect you to transfer as video, 24 usually should be slightly pulled down to 23.976 and edited that way. And if doing so, your audio should be pulled down also (the same 1000/1001 % amount). And if one is then taking a 23.976 and Telecine-ing it with 3:2 pulldown, then it would go to 29.97. But if this person/group went straight to 29.97, without doing the proper adjustment, there is quite a good chance that there might be a skipped or dropped or frozen or black frame(s) stuck in there, depending upon the conversion algorithm (incl. interpolate/blend).

    Was the black screen throughout the whole piece, or in certain section, or just at the end? If the whole piece, that sounds like there is an incompatibility between your output codec (and settings) and their decoding system (and settings). Hard to tell at this point who would be at fault.

    Out of curiosity, are you exporting via OMF or AAF out of PT (with embedded media), or are you just rendering consolidated stems using the original reference vid clip (externally)?

    Scott (a 25+ year veteran PT user).
    Last edited by Cornucopia; 16th Apr 2018 at 22:36.
    Quote Quote  

Similar Threads