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sunkast  
#1 Posted : Sunday, September 16, 2018 9:15:53 PM(UTC)
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I have set my recorder to use MP4 with hardware encoding so that I can reduce the load on the CPU in my PC. However using hardware encoding sets the video to variable framerate. While this is nice for the file size, unfortunately when I go to edit the video, it imports it at 100FPS rather than 59.94. While I could change the project settings to 59.94FPS, this is less than ideal since in essentially doubles the time it takes to render out the video after editing.

Is there a way to record using hardware encoding but set it to be a constant frame rate, rather than variable?
DWAM  
#2 Posted : Monday, September 17, 2018 2:34:14 AM(UTC)
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???

I'm not sure what you're talking about, I have never seen vMix recording something else than the framerate you set for recording, neither with GPU or CPU. The bitrate might vary but not the framerate...
Check your settings in vMix...

Also check your files with a tool like mediainfo to make sure about the framerate.

I guess your issue is most likely related to your NLE (which you did not mention btw)

Guillaume
admin  
#3 Posted : Monday, September 17, 2018 5:38:19 AM(UTC)
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Hi,

vMix only records at a fixed frame rate for all formats.
Potential reasons for it showing up incorrectly in a video editor may be due to dropped frames
(which will be noted in the vMix recording log and might be due to a slow graphics card or other system performance issue) or some other compatibility issue with the video editor.

What video editors have you tried?

Regards,

Martin
vMix

sunkast  
#4 Posted : Tuesday, September 18, 2018 12:14:18 PM(UTC)
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Updated my editor to the latest version and that seemed to fix it.

But for the record, MediaInfo does show that the encoded video is VBR.

Frame rate mode : Variable
Frame rate : 59.608 FPS
Minimum frame rate : 11.988 FPS
Maximum frame rate : 60.000 FPS

For comparison, the video that I recorded without hardware encoding:

Frame rate mode : Variable
Frame rate : 59.940 FPS
Minimum frame rate : 59.940 FPS
Maximum frame rate : 60.000 FPS
ovinas  
#5 Posted : Tuesday, September 18, 2018 1:14:05 PM(UTC)
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Just for the record ;-) but...
VBR = Variable Bit Rate
What you're talking about is VFR.

VBR ≠ VFR

https://en.wikipedia.org/wiki/Variable_bitrate
https://en.wikipedia.org/wiki/Variable_frame_rate
admin  
#6 Posted : Tuesday, September 18, 2018 1:38:10 PM(UTC)
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That is quite strange, here is a mediainfo on a MP4 recording in vMix I just did:

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L4
Format settings : 1 Ref Frames
Format settings, CABAC : No
Format settings, RefFrames : 1 frame
Format settings, GOP : M=1, N=29
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 10 s 878 ms
Bit rate : 135 kb/s
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 (29970/1000) FPS
on_call  
#7 Posted : Saturday, December 15, 2018 1:41:40 AM(UTC)
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MP4 recording is 100% VFR (variable frame-rate). I'm currently dealing with that headache and all it entails right now.

I record separate audio for quality, but also because vMix likes to insert dropped audio every time a new clip is created in a continuous recording. I guess I'll be using highly compressed USB audio instead of my clean recorder audio.
admin  
#8 Posted : Saturday, December 15, 2018 7:07:27 PM(UTC)
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Originally Posted by: on_call Go to Quoted Post
MP4 recording is 100% VFR (variable frame-rate).


This extremely unlikely, as our previous comments in this thread have confirmed.
If you believe you have a variable frame rate MP4 recorded directly in vMix, please first confirm it is so using the latest MediaInfo
and then email it to us at info@vmix.com.au.

Maybe a hardware encoder is overwriting the vMix internal recording settings, though it seems unlikely.

Regards,

Martin
vMix
Laimiuz  
#9 Posted : Saturday, March 20, 2021 4:13:46 AM(UTC)
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Originally Posted by: admin Go to Quoted Post
Originally Posted by: on_call Go to Quoted Post
MP4 recording is 100% VFR (variable frame-rate).


This extremely unlikely, as our previous comments in this thread have confirmed.
If you believe you have a variable frame rate MP4 recorded directly in vMix, please first confirm it is so using the latest MediaInfo
and then email it to us at info@vmix.com.au.

Maybe a hardware encoder is overwriting the vMix internal recording settings, though it seems unlikely.

Regards,

Martin
vMix


I had the same problem yesterday. I put my video card to another slot and did not had enough time to test the system. It was simple project: 2 CAM's via SDI, 2 PC's via NDI, also 2 SDI and 2 NDI Outputs. I decided to make a record H.264 at 28Mbps in vMix. All the time I watched resources in vMix and in Task Manager Performance - CPU about 18% (Xeon 2686 v3), GPU about 58%. Almost at the end of the show I found, that I have some audio glitches on SDI Out (we used SDI as video return to camera mans only). Then I saw strange numbers in the recording area - last digit was probably recorded frames, but first always jumped between 18 and 46 (vMix project 50FPS). When the show ended I tried to play recorded files with various players (vMix, VLC, QuickTime, WMP) but result was the same - about half a second faster video, half a second freeze frame. All files in the same "sequence". Today from early morning I started to search a problem and found, that only the first slot of PCIe in my motherboard (ASUS X99 WS-E) supports 16 lanes. I'm not sure for 100%, but I think that was the problem. Simply it was not enough internal resources to handle smooth 50FPS internal data throughput somewhere in VGA - CPU chain...
When I started to analyze recorded files, they all recorded in peak framerate mode. I tried to convert them to Constant Frame Rate. Looks a way better, but not enough for broadcastring :(
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