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Activity Forums Compression Techniques Compressing an MP4 of 1.5% talking head, 98.5% static images

  • Compressing an MP4 of 1.5% talking head, 98.5% static images

  • Steve Roberts

    December 26, 2021 at 10:10 pm

    I’m compressing a 33-minute (1440×900, 25 fps) video in Premiere Pro, for online delivery. The first 30 seconds is a talking head, and the rest is composed of still images. It’s basically a narrated slide show with an introduction by the presenter, Zoom-style.

    I was provided with his original clip, and he asked me to make a couple of cuts. However, I’m having trouble with the compression.

    His original 34-minute clip came in around 55MB, H.264. But I can’t approach that file size without losing too much quality, compared to the original.

    I’d love to keyframe the compression, which I recall doing back in the day with Premiere 4.1, to set a high rate for the intro, and low for the stills. Not sure if I can still do that.

    How could I get a low file size, but high quality for the talking head intro?

    (I’ve used 2-pass VBR, target .25 Mbps, max 20Mbps, audio AAC-44-128, Max quality, KF distance 45, but the file is around 96 MB and the result is blockier than the original.)

    Edit: it’s been a while since I’ve worked with highly-compressed source, so if I have to accept this degree of generational loss, sure.

  • Craig Seeman

    December 26, 2021 at 10:23 pm

    When you say “original clip” please explain. What codec? You mention the “original clip” being 55MB H.264. Using that clip would be a problem.

    You would need the source for their compression, ideally ProResHQ or some equivalent at the source frame size.

    Have you examined the compressed clip in something like Media Info to see what their compression settings were?

    Some encoders are better than others. Do you know what encoder they used?

  • Steve Roberts

    December 26, 2021 at 10:48 pm

    Thanks for the quick reply, Craig.

    Yep, 55MB H.264, recorded by my friend via Zoom, is the original source, unfortunately: laptop camera over Zoom. Hence, the problem. 🙂

    I’ve examined the data rate in Mediainfo (thanks for the pointer), and overall, it’s 216Kbps, video is 87.6 Kbps H.264/AVC, audio is 126 Kbps.

    Zoom might use a proprietary encoder, or settings, so I might have to accept a much higher file size for acceptable quality, I think.

  • Craig Seeman

    December 27, 2021 at 2:35 am

    Is the 55MB file a Zoom recording?

    Are you re-editing that file?

    Ugh. Zoom has a highly compressed recording format with a very difficult GOP structure that generally is a problem for NLEs. Zoom has a NLE compatible mode that one is supposed to use if the file is to be edited later.

    The file will be very small but difficult to edit. You should convert to Apple ProRes. Baring their extreme encoder settings, it will be difficult for you to compress that small with that quality. BTW you can see the actual GOP structure and frame by frame bit rate in Telestream Switch Pro. Ideally you’d want multipass, High Profile, CABAC entropy but it would be difficult to match their very sparse keyframes.

  • Steve Roberts

    December 27, 2021 at 9:17 am

    Yeah. Zoom. Ugh.

    Thanks very much for the compression spec. I’ll also ask my friend to set that NLE-compatible switch should he ever want to do this again.

    In the end, I gave him (before reading your last post) a decent looking file that was around 225 MB. He was happy.

    Thanks again.

  • Craig Seeman

    December 27, 2021 at 4:48 pm

    Sounds like you did your best under the circumstances.

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