Zoom recording hangs QSF

musicvid

Member
I have a client's Zoom recording that causes the lightning bolt to turn yellow and the clock to run on when I QSF at the default Fast Stream Copy settings.

When I recode it, it seems to run OK.

General
Complete name :C:\Users\Mark\Downloads\zoom_0 (1).mp4
Format :MPEG-4
Format profile :Base Media / Version 2
Codec ID :mp42 (isom/mp42)
File size :364 MiB
Duration :55 min 59 s
Overall bit rate mode :Variable
Overall bit rate :909 kb/s
Encoded date :UTC 2021-09-09 08:10:44
Tagged date :UTC 2021-09-09 08:10:44


Video
ID :2
Format :AVC
Format/Info :Advanced Video Codec
Format profile :High@L5
Format settings :CABAC / 11 Ref Frames
Format settings, CABAC :Yes
Format settings, Reference frames :11 frames
Codec ID :avc1
Codec ID/Info :Advanced Video Coding
Duration :55 min 59 s
Bit rate :780 kb/s
Width :1 280 pixels
Height :720 pixels
Display aspect ratio :16:9
Frame rate mode :Constant
Frame rate :25.000 FPS
Color space :YUV
Chroma subsampling :4:2:0
Bit depth :8 bits
Scan type :Progressive
Bits/(Pixel*Frame) :0.034
Stream size :312 MiB (86%)
Title :H.264/AVC video
Encoded date :UTC 2021-09-09 08:10:44
Tagged date :UTC 2021-09-09 08:10:44
Codec configuration box :avcC


Audio
ID :1
Format :AAC LC
Format/Info :Advanced Audio Codec Low Complexity
Codec ID :mp4a-40-2
Duration :55 min 59 s
Bit rate mode :Variable
Bit rate :126 kb/s
Maximum bit rate :161 kb/s
Channel(s) :1 channel
Channel layout :C
Sampling rate :32.0 kHz
Frame rate :31.250 FPS (1024 SPF)
Compression mode :Lossy
Stream size :50.6 MiB (14%)
Title :AAC audio
Encoded date :UTC 2021-09-09 08:10:44
Tagged date :UTC 2021-09-09 08:10:44
 

Dan203

Senior Developer
Staff member
Try this. Hold Shift and click Tools->Options. Look for option "Max GOP Length (secs)" around #51. Double the value. Now try QSFing the file again.
 

Dan203

Senior Developer
Staff member
OK good. That setting triggers a buffer size increase for the audio filters in the output graph. I could see from your log that the audio filter was filling up and stalling while the video filter was empty so I was hoping that would help, but wasn't sure how high you would need to go.
 

musicvid

Member
Good Catch! There are a few things "odd" about these Zoom files, including single-channel audio and 11 Ref frames, despite substandard video bitrate. Maybe a preset to make them "normal" mp4 (whatever that is)? I'll run some tests; I've got extra time on my hands and a handful of Zoom recordings.
 
Last edited:

Dan203

Senior Developer
Staff member
Wow. That's excessive. But I guess if you're trying to minimize bandwidth and you're mostly transmitting talking heads it's probably fine for the streaming portion.
 

musicvid

Member
Yes, they've pulled some tricks to get "acceptable" results at suboptimal bitrates. I ran ffprobe and got one I-frame followed by 899 P-frames and 0 B-frames. 780 Kbps, which is low even for talking heads.
 
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