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| Ronio Primo |
| Posted: Nov 11 2013, 06:48 AM |
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Saving files append to the beginning of the movies the selected frame on the timeline.
Windows XP SP 3.
VirtualDub 1.10.3 (exp.) e 1.10.4. |
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| dloneranger |
| Posted: Nov 11 2013, 07:06 AM |
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Never seen that happen
What you do see all the time though is b-frame effect of a delay between moving frames and your actual position
If you're video uses b-frames there's normally a visual delay when moving to keyfames and then forward (equal to the number of b-frames in the video stream at that position)
When you jump position to a keyframe the codec needs previous frames to make the complete picture, but by jumping to a keyframe the codec isn't given any previous frames, so it's can immediately display what you should see and delays the picture until it has enough frames to generate a complete picture
That's the reason you can often see the first frame or two shown as green or black when you know you started with an actual image.
You can check for that by moving to the first frame, holding shift-rightarrow (on the keyboard) until the frames starts jumping position rapidly as you move to the next keyframe. Then press rightarrow by itself a few times - the frames should still jump a few times before starting to moving frame by frame. That's the b-frame delay in action and you also see it when you move back to the beginning of the video and go forwards a few frames.
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| Ronio Primo |
| Posted: Nov 11 2013, 11:00 AM |
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Either way it's annoying. You can delete?
Waiting for a quick fix Thank you in advance and I offer a warm greeting!
Ronio Primo |
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| dloneranger |
| Posted: Nov 11 2013, 03:17 PM |
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There isn't anything to fix if it's that effect (not without a major rewrite I'd guess)
(if you open a new virtualdub and load the video, you don't get a frame from the middle of the film)
It's just a visual anomaly of editing that kind of video due to the limitations of VFW that virtualdub uses - it's 1 frame in = 1 frame out doesn't play nicely with codecs that use frames from the past and future timeline
You can open the video with the directshow plugin and it should behave - although that always decompresses to uncompressed audio/video, which may not be what you want
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| meowmeow |
| Posted: Nov 13 2013, 05:33 AM |
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When opening x264 videos the first few frames are always was black, now they're green.
With last frames dropped. 6 frames lost. More B-frames, more loss.
These first "empty" frames occasionally filled from buffer when user seeking other frames. And so encoded, like that, with garbage in beginning of a video!
What's more annoying, this error occurs later too, overwriting frames with older data as of wrong frame # - even distant keyframes. Until buffer overloaded.
directshow plugin helps, but it's slower at seeking. |
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| dloneranger |
| Posted: Nov 13 2013, 06:10 AM |
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The green frame is from the codec itself - it's going "i don't have enough information to show a complete picture yet, so here's a green one" (some codecs give a black one instead, so maybe you're using a different codec now)
It's a delay between what frame is being decoded and when the codec has enough frames to be able to display it
It's due to b-frames and virtualdub using vfw codecs
Directshow codecs can scan through the file to get the future frames and use them to decode the current frame
VFW demands 1 frame in, 1 frame out
For this reason, b-frames are only recommended for the final encoding
I have no idea what 'buffer overflow' your talking about though
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| meowmeow |
| Posted: Nov 13 2013, 09:00 AM |
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| QUOTE (dloneranger @ Nov 13 2013, 06:10 AM) | | For this reason, b-frames are only recommended for the final encoding |
I guess, I just won't use b-frames at all. Final videos just don't exists in this world.
Now XviD, and even x254vfw works perfectly! Thank you! |
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| -vdub- |
| Posted: Nov 13 2013, 07:15 PM |
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I read often in the past with xvid and some x264 many thought it's better to use no B-frames maybe the same they find with x264. Reasons they gave was for better compression and smaller video size they also gain for having no green frames from what is said here. I need to try this next time that I have green frame problem using compressed or uncompressed video like the one I recently had |
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| dloneranger |
| Posted: Nov 13 2013, 08:06 PM |
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You can get around them with the DirectShow plugin (and I think the ffmpeg one as well iirc)
But then you get uncompressed video/audio, which many not be what you want
BFrames are just a size/quality efficiency, without them, you'll just get 1) a bit larger file, or 2) slightly worse quality
It's possible you may not even be able to see a quality difference and that file size difference may be small - all depends on the source really
Though most people seem to encode with 2 pass fixed bitrates for some bizarre reason so quality's already taken a back seat
X264vfw's zero latency option turns off bframes, and in xvid you can set them to 0 to disable them
Directshow works fine because the DirectShow system can skip backwards and forwards to get all the bits it needs to produce 1 output frame
(as mentioned it's slower seeking than avi in virtualdub though)
Btw if anyones going to encode with XVid, make sure to tick it's start with an I frame option as well :-)
There's also a useful program called mpeg4modifier than can alter divx/xvid encoded videos to use packed/unpacked bitstreams
And that gets around the jumping frame problem
Divx wants packed bitstreams, xvid and ffdshow prefer unpacked bitstreams
It's a lossless operation and quite fast
http://www.moitah.net
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| dloneranger |
| Posted: Nov 13 2013, 09:51 PM |
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There's an x264vfw encoded sequence I did of just the frame number on each frame that's quite good at showing what's actually happening as you move around when the bframes bite
https://dl.dropboxusercontent.com/u/1702491...umbers%20B8.avi (92K)
A good example is to start at the beginning, step a few frames to the right, then step a fre keyframes to the right and then a few more frames to the right
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| meowmeow |
| Posted: Nov 14 2013, 03:02 AM |
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| QUOTE (dloneranger @ Nov 13 2013, 08:06 PM) | | X264vfw's zero latency option turns off bframes, and in xvid you can set them to 0 to disable them |
"--tune zerolatency" a little too much. Best for real-time capturing.
Option "-b 0" does what we need. Then use x264vfw internal libav decoder from this build http://sourceforge.net/projects/x264vfw/files/
While windows still can use any decoder it likes. |
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