I am provided surveillance video footage from a bus that I need to use for photogrammetry purposes. Understanding pixel aspect ratio, frame rate, and synchronization is therefore very important. The video is provided to me in a .video file and I am given an executable that displays all the bus cameras' videos. Here is the forward facing camera: https://www.securityinformed.com/mobileview-forward-facing-camera-cctv-camera-technica...opup#more-info
The other cameras are a different type.
To get the video out, I start with ffmpeg. Here is the data from ffprobe:
[Attachment 66982 - Click to enlarge]
For some reason, ffmpeg/ffprobe do not display the PAR or the DAR as I would like to see.
What can I infer from the 704x480 video size? Is this a 4CIF video? The camera specs state that it is NTSC and Digital DSP, so I don't think it is capturing analog and then converting to digital. I believe these are "IP cameras" recorded using an "NVR." I have another video from the same bus and the same camera system that only exports at 352x240.
What does the 720X540 "Picture Elements" spec mean in the camera specs? Can I relate this to the 520 TVL resolution, or the 1/3" sensor size? I know that a 1/3" sensor is in 4:3 format. Does this mean that this particular 1/3" sensor has 720X540 picture sensing elements? I feel like I read in most specs that a 1/3" sensor has 640x480 picture sensing elements.
I use this command: ffmpeg -i [INPUT_FILENAME].video -map 0:N -c:v copy [OUTPUT_FILENAME].mp4 to get the video streams out. Stream 4 is the forward facing camera.
Upon export I get the following warnings:
[Attachment 66983 - Click to enlarge]
What do they mean? Is there any way to access the original timestamps?
Looking at the details of the video, it was exported at 30.30 frames/second. Why not 29.97 fps tbr or 30 fps tbc? When I load the video into Camtasia, the behavior is extremely odd. It will pause and then play, pause and then play, etc. How can I fix this?
When I look at MediaInfo, it says the display aspect ratio is 3:2. Shouldn't it be 4:3 for standard definition? Further, it says 15 fps. What happened to my 29.97 fps and/or 30 fps of data?
[Attachment 66984 - Click to enlarge]
When rendered in a video player, the aspect ratio is 704/480 and things look a little squat. Does this mean it is displaying square pixels? When I capture a still using MPC-HC and open it in Zoominterpolation, I see rectangular pixels with an aspect ratio that appears more geometrically correct. Does Zoominterpolation know that the PAR is 0.909090...? If so, how come I can't see this in any of the data from MediaInfo or ffmpeg? Or is it simply assuming that since I have 704x480 it must have a PAR of 0.9090?
[Attachment 66985 - Click to enlarge]
I am also interested in synching the other videos as well as the audio but that's a question for another day...
+ Reply to Thread
Results 1 to 1 of 1