Rendered video randomly twice as fast as audio (preview looks normal) #47786

New Issue

Natalie Ardasevova · 2016-03-14T00:07:24+01:00

2016-03-14 00:07:24 +01:00

System Information
RHEL 7.1 (Maipo)
Graphics: Intel® HD Graphics 5500 (Broadwell GT2)

Blender Version
Broken: (blender-2.76b-linux-glibc211-x86_64)

Short description of error

Dear all, a very strange thing is happening to me in blender. I recorded footage from cca 10 years old camera (can't tell you the type, don't remember). The footage was 25fps, original dimension 1440x1080. I set up the blender environment according to this video https://www.youtube.com/watch?v=yjTn8GsRk48&list=PLjyuVPBuorqIhlqZtoIvnAVQ3x18sNev4&index=2 and started inserting my clips. As the tutorial said, I was supposed to match the dimensions and fps of the original with the settings in Blender. But when I changed the Blender's preset resolution of 1920x1080 to my needed 1440x1080, the video got squeezed from right and left, leaving the picture squeezed and therefore useless. So I changed it back, hoping it wouldn't matter (but it may affect the problem I'm about to describe).

I had footage that was all taken from one camera under the same settings. When I took pieces of the recording and cut them in Blender, after rendering, in a few of these cuts the video is twice as fast as the audio. Later I deleted and inserted the "wrong" pieces again. The strangest thing is that one day it rendered fine, and a few days later the latter clip is wring again:
You can see here:
everything at the right speed - http://www.filedropper.com/8168-9085
second cut is wrong - http://www.filedropper.com/8700-9921

Could you tell what went wrong from this?

Also - is it on purpose that when closing Blender, it doesn't ask if I want to save changes or not?

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

treti pokus.blend

Thank you...

**System Information** RHEL 7.1 (Maipo) Graphics: Intel® HD Graphics 5500 (Broadwell GT2) **Blender Version** Broken: (blender-2.76b-linux-glibc211-x86_64) **Short description of error** Dear all, a very strange thing is happening to me in blender. I recorded footage from cca 10 years old camera (can't tell you the type, don't remember). The footage was 25fps, original dimension 1440x1080. I set up the blender environment according to this video https://www.youtube.com/watch?v=yjTn8GsRk48&list=PLjyuVPBuorqIhlqZtoIvnAVQ3x18sNev4&index=2 and started inserting my clips. As the tutorial said, I was supposed to match the dimensions and fps of the original with the settings in Blender. But when I changed the Blender's preset resolution of 1920x1080 to my needed 1440x1080, the video got squeezed from right and left, leaving the picture squeezed and therefore useless. So I changed it back, hoping it wouldn't matter (but it may affect the problem I'm about to describe). I had footage that was all taken from one camera under the same settings. When I took pieces of the recording and cut them in Blender, after rendering, in a few of these cuts the video is twice as fast as the audio. Later I deleted and inserted the "wrong" pieces again. The strangest thing is that one day it rendered fine, and a few days later the latter clip is wring again: You can see here: everything at the right speed - http://www.filedropper.com/8168-9085 second cut is wrong - http://www.filedropper.com/8700-9921 Could you tell what went wrong from this? Also - is it on purpose that when closing Blender, it doesn't ask if I want to save changes or not? **Exact steps for others to reproduce the error** Based on a (as simple as possible) attached .blend file with minimum amount of steps [treti pokus.blend](https://archive.blender.org/developer/F290086/treti_pokus.blend) Thank you...

Natalie Ardasevova commented

2016-03-14 00:07:24 +01:00

Changed status to: 'Open'

Natalie Ardasevova commented

2016-03-14 00:07:24 +01:00

Added subscriber: @Natwhipu

david mcsween commented

2016-03-14 01:37:30 +01:00

Added subscriber: @davidmcsween

david mcsween commented

2016-03-14 01:37:30 +01:00

If the source media was anamorphic and your *player does not support PAR //(Pixel Aspect Ratio) then it will look squeezed.
"The HDV 1080i/p formats record at 1440×1080 resolution with a 1.333 PAR, so these would be considered anamorphic HD formats. Note that 1440 times 1.333 equals 1920, so when this video is played back from an appropriate device like an HDV camera or a Blu-ray player, the device will respect the 1.333 PAR and display the video at 1920×1080, while Windows Media Player would display the image at the native 1440×1080 size using square pixels, losing the widescreen appearance. "

When you selected the alternate project dimensions you also chose a different frame rate. However it is only 23.98fps, not enough to account for a doubling of the frame rate. I think that the problem could be with the source media CODEC. It could be Frame Segmented which is sort of interlaced progressive. Blender might not recognize this format correctly and may play each segment as a separate frame. This will make the sound appear to run faster than the video.
However due to the incorrect decoding Blender might display to few frames as well.

I would transcode this media to a more modern CODEC that Blender can recognize. Also try generating a proxy and timecode. You can use ffmpeg or MpegStreamclip to do this. If this resolves the issue then it probably isn't a bug, just an unsupported legacy CODEC.

If the source media was [anamorphic ](http:*blog.sharbor.com/blog/2010/07/anamorphic-widescreen-understanding-pixel-aspect-ratios-3/) and your ***player does not support PAR //**(Pixel Aspect Ratio) then it will look squeezed. "The HDV 1080i/p formats record at 1440×1080 resolution with a 1.333 PAR, so these would be considered anamorphic HD formats. Note that 1440 times 1.333 equals 1920, so when this video is played back from an appropriate device like an HDV camera or a Blu-ray player, the device will respect the 1.333 PAR and display the video at 1920×1080, while Windows Media Player would *display the image at the native 1440×1080 size using square pixels, losing the widescreen appearance*. " When you selected the alternate project dimensions you also chose a different frame rate. However it is only 23.98fps, not enough to account for a doubling of the frame rate. I think that the problem could be with the source media CODEC. It could be Frame Segmented which is sort of interlaced progressive. Blender might not recognize this format correctly and may play each segment as a separate frame. This will make the sound appear to run faster than the video. However due to the incorrect decoding Blender might display to few frames as well. I would transcode this media to a more modern CODEC that Blender can recognize. Also try generating a proxy and timecode. You can use ffmpeg or MpegStreamclip to do this. If this resolves the issue then it probably isn't a bug, just an unsupported legacy CODEC.

Natalie Ardasevova commented

2016-03-17 12:18:10 +01:00

Hi David,

thank you so much for your quick reply! Sweet, I downloaded ffmpeg. Can I ask you what "more modern CODEC" would you recommend using that Blender 2.76 would recognize?

Thank you,

Natalie

Hi David, thank you so much for your quick reply! Sweet, I downloaded ffmpeg. Can I ask you what "more modern CODEC" would you recommend using that Blender 2.76 would recognize? Thank you, Natalie

david mcsween commented

2016-03-17 23:55:23 +01:00

Hi Natalie, you may have a long recording in which case i might suggest mp4 codec. The key thing is to transcode the frames in their correct interlacing so that no resolution is lost and you get square pixels without anamorphic squeezing. In blender every function of the timeline may cost you rendering time.. which can multiply pretty quickly over a long project. You want to avoid scaling which the vse does automatically when project settings don't match the source.

David

Hi Natalie, you may have a long recording in which case i might suggest mp4 codec. The key thing is to transcode the frames in their correct interlacing so that no resolution is lost and you get square pixels without anamorphic squeezing. In blender every function of the timeline may cost you rendering time.. which can multiply pretty quickly over a long project. You want to avoid scaling which the vse does automatically when project settings don't match the source. David

Sergey Sharybin commented

2016-03-22 16:21:42 +01:00

Added subscriber: @Sergey

Sergey Sharybin commented

2016-03-22 16:21:42 +01:00

This is tricky to troubleshoot.. We really need to have reproduceable case for troubleshooting. Simpler the case is better. It'll also help if you isolate the randomness, if something is random we wouldn't know if we're unlucky and random is bad for us or the issue could not be reproduced on our machines.

Additionally. try using Record Run timecode for your videos and see if makes any difference.

If timecode doesn't help, please provide all files needed to reproduce the issue.

This is tricky to troubleshoot.. We really need to have reproduceable case for troubleshooting. Simpler the case is better. It'll also help if you isolate the randomness, if something is random we wouldn't know if we're unlucky and random is bad for us or the issue could not be reproduced on our machines. Additionally. try using Record Run timecode for your videos and see if makes any difference. If timecode doesn't help, please provide all files needed to reproduce the issue.

Aaron Carlisle commented

2016-03-25 22:22:19 +01:00

Added subscriber: @Blendify