$:andre\> wget -vv https://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Hym_-_2015-06-25.webm/800px--Hym_-_2015-06-25.webm.jpg--2015-11-01 17:46:33-- https://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Hym_-_2015-06-25.webm/800px--Hym_-_2015-06-25.webm.jpg Resolving upload.wikimedia.org (upload.wikimedia.org)... 184.108.40.206, 2620:0:862:ed1a::2:b Connecting to upload.wikimedia.org (upload.wikimedia.org)|220.127.116.11|:443... connected. HTTP request sent, awaiting response... 429 Too Many Requests 2015-11-01 17:47:17 ERROR 429: Too Many Requests.
Ok, testing in isolation on a vagrant setup.... the thumbnailing via ffmpeg works, but can take like a full minute to create. o_O
If I'm reading output from mkvinfo correctly, it seems to have only 2 keyframes in the entire file -- so it's probably decoding half the file up to the midpoint to get the output frame. :(
Well it is transcoded from a lossless avi by ffmpeg (two pass transcoding) with ""ffmpeg.exe" -i infile -c:v libvpx-vp9 -pass 1 -aspect 16:9 -b:v 12000K -crf 10 -threads 8 -speed 4 -tile-columns 6 -frame-parallel 1 -an -f webm
ffmpeg.exe" -i infile -c:v libvpx-vp9 -pass 2 -b:v 12000K -crf 10 -aspect 16:9 -threads 8 -speed 2 -tile-columns 6 -frame-parallel 1 -auto-alt-ref 1 -lag-in-frames 25 -an -f webm outfile.webm"
I also used these settings on a few other but shorter (e.g. File:Trichterspinne mit Beute -2015-06-14.webm) uploads. In fact the creation of the thumbnail seems to take a significant longer time than using the vp8 codec.
@Pristurus ok I've found a couple other references to keyframe issues with ffmpeg vp9 output, and am seeing similar behavior on a couple of files I encoded myself as well. I'll try fiddling with the settings and see if I can resolve it by forcing more keyframes...
Note that the file also can't be seeked during playback due to the lack of keyframes. (If you get the vp8 or theora transcodes they seek fine, but the original doesn't)
Fine! As far as I know this parameter is used to set the maximum interval between keyframes. So the real size of intervals will be different from this value. Why do you prefer a value of 128? I think it should depend on the framerate of the input video. Otherwise it will produce in a 60fps file a new keyframe after about 2 seconds and in a 24fps file after about 5 seconds (theoretical maximum).