SI footage on Youtube at

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Silicon Imaging SI-2K
2/3" 1080p IT-integrated 10-bit digital cinema w/direct-to-disk recording.

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Old February 6th, 2009, 06:24 PM   #1
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Location: Akron, Ohio
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SI footage on Youtube

I uploaded a quick 90sec SI-2K clip on YouTube just for fun. Click the ‘watch in HD' link.

I’m actually new to YouTube and can’t figure out why some HD videos play smooth and some buffer every five seconds or so. Doesn’t YouTube recompress to its own format anyway?

Original Format- 10-bit Cineform RAW 2K
23.97p with 1/47.97 shutter
Kodak 250D LUT
Nikkor Primes (I think I used a 35mm, 50mm and 60mm macro)
Overcast Day- K5600 temp
Zero Sharpening applied

Uploaded to YouTube as- H.264
6000k 2-pass
128k audio


Last edited by John DeLuca; February 7th, 2009 at 09:54 AM. Reason: New YouTube Link
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Old February 6th, 2009, 07:00 PM   #2
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Yes, Youtube recompresses everything now (used to be you could circumvent their system by compressing your own FLV, but they've long since closed that loophole). Flash video with MP3 audio for the normal and high quality files, H.264 video with AAC audio in an MP4 container for HD material.

I've had that buffering problem on some videos, but it seems to occur randomly. The most obvious cause is that the video is playing faster than the file can be downloaded, and the player reaches the end of the available data. The simple solution for that is to pause playback and let the file finish transferring. I have, however, seen cases where the file just won't load any further than the cursor unless I actually hit play, turning Youtube's usual progressive download design into what's essentially streaming video. Sometimes it's fast enough to play smoothly, sometimes not. The only real solution is to reload the page, pause the video again, and hope for the best. I couldn't tell you the actual cause, though.

Regardless, I didn't get this with your video, and though I don't keep up with SI news, the footage was gorgeous! I noticed a bit of stuttering, however, even once the file was completely loaded. If you haven't already, I'd suggest forcing a keyframe every so many frames (twenty four, in this case) during compression. I can't say for sure how Youtube's servers work with uploads, but I've had the stuttering myself in the past, and using a smaller GOP seems to help.
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Old February 7th, 2009, 10:18 AM   #3
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Thanks for the feedback. I re-compressed/swapped out the file with much better results. I’m actually quite impressed with YouTube’s ‘HD’, I avoided joining for years due to the poor quality.

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