# Dropped frames in video recording

**URL:** <https://forum.opencv.org/t/dropped-frames-in-video-recording/14900>\
**Category:** Python\
**Tags:** videoio\
**Created:** [October 17, 2023, 10:27pm UTC](https://forum.opencv.org/t/dropped-frames-in-video-recording/14900 "2023-10-17T22:27:34Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![KORDESTANY](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/kordestany/32/8909_2.png) [@KORDESTANY](https://forum.opencv.org/u/KORDESTANY)\
**Post date:** [October 17, 2023, 10:27pm UTC](https://forum.opencv.org/t/dropped-frames-in-video-recording/14900/1 "2023-10-17T22:27:34Z")

</div>

Hi everyone,  
I have a Logitech Webcam C270 supporting YUYV 1280x720@10 FPS and Motion-JPEG 1280x720@30 FPS according to the output from “v4l2-ctl --list-formats-ext”.

I am trying to record 1280x720@30 FPS with the code below; however, the recorded video length is ~ 20% to 50% shorter than the real-time. My explanation is Python is not fast enough to capture all the frames, but would like someone with more experience to confirm this.  
(The workstation is a Ubuntu 22.04.3, 16-core CPU, 32G of RAM. )

**Code:**

frame\_width = 1280  
frame\_height = 720  
frame\_rate = 30 # I have changed this from 15 to 30, with the results below.  
capture\_duration = 10

cap = cv2.VideoCapture(0, cv2.CAP\_V4L2)

if (cap.isOpened() == False):  
print(“Unable to access camera”)

cap.set(cv2.CAP\_PROP\_FOURCC, cv2.VideoWriter\_fourcc(‘M’,‘J’,‘P’,‘G’))  
cap.set(cv2.CAP\_PROP\_FRAME\_WIDTH, frame\_width)  
cap.set(cv2.CAP\_PROP\_FRAME\_HEIGHT, frame\_height)  
cap.set(cv2.CAP\_PROP\_FPS, frame\_rate)  
time.sleep(1)

print(f"Width: {cap.get(cv2.CAP\_PROP\_FRAME\_WIDTH)}“)  
print(f"Height: {cap.get(cv2.CAP\_PROP\_FRAME\_HEIGHT)}”)  
print(f"FPS: {cap.get(cv2.CAP\_PROP\_FPS)}")

fileName = f"out{frame\_width}x{frame\_height}@{frame\_rate}.avi"  
print(f"Saving to: {fileName}")

out = cv2.VideoWriter(fileName,  
cv2.VideoWriter\_fourcc(‘M’,‘J’,‘P’,‘G’),  
frame\_rate,  
(frame\_width,frame\_height))

start\_time = time.time()  
while( int(time.time() - start\_time) \<= capture\_duration ):  
ret, frame = cap.read()

if not ret:  
break

frame = cv2.putText(frame, str(datetime.datetime.now()),  
(50, 50),cv2.FONT\_HERSHEY\_SIMPLEX, 1,  
(255, 255, 255), 2, cv2.LINE\_AA)

out.write(frame)

cap.release()  
out.release()

**Results:**

$ ffprobe out **1280x720@15**.avi 2\>&1 | grep “Duration|Stream”  
Duration: **00:00:10.67** , start: 0.000000, bitrate: 8904 kb/s  
Stream #0:0: Video: mjpeg (Baseline) (MJPG / 0x47504A4D), yuvj420p(pc, bt470bg/unknown/unknown), 1280x720, 8952 kb/s, 15 fps, 15 tbr, 15 tbn

$ ffprobe out **1280x720@20**.avi 2\>&1 | grep “Duration|Stream”  
Duration: **00:00:08.05** , start: 0.000000, bitrate: 12437 kb/s  
Stream #0:0: Video: mjpeg (Baseline) (MJPG / 0x47504A4D), yuvj420p(pc, bt470bg/unknown/unknown), 1280x720, 12501 kb/s, 20 fps, 20 tbr, 20 tbn

$ ffprobe out **1280x720@30**.avi 2\>&1 | grep “Duration|Stream”  
Duration: **00:00:05.37** , start: 0.000000, bitrate: 18467 kb/s  
Stream #0:0: Video: mjpeg (Baseline) (MJPG / 0x47504A4D), yuvj420p(pc, bt470bg/unknown/unknown), 1280x720, 18556 kb/s, 30 fps, 30 tbr, 30 tbn

It seems ffmpeg can record from this camera as:  
$ ffmpeg -t 10 -f video4linux2 -input\_format mjpeg -framerate 30 -video\_size 1280x720 -i /dev/video0 out.avi

$ ffprobe out.avi 2\>&1 | grep “Duration|Stream”  
Duration: **00:00:10.00** , start: 0.000000, bitrate: 434 kb/s  
Stream #0:0: Video: mpeg4 (Simple Profile) (FMP4 / 0x34504D46), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 425 kb/s, 30 fps, 30 tbr, 30 tbn, 30 tbc

Thanks for your time.