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POPipe raw OpenCV images to FFmpeg
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copied!<p>Here's a fairly straightforward example of reading off a web cam using OpenCV's python bindings:</p> <pre><code>'''capture.py''' import cv, sys cap = cv.CaptureFromCAM(0) # 0 is for /dev/video0 while True : if not cv.GrabFrame(cap) : break frame = cv.RetrieveFrame(cap) sys.stdout.write( frame.tostring() ) </code></pre> <p>Now I want to pipe the output to ffmpeg as in:</p> <pre>$ python capture.py | ffmpeg -f image2pipe -pix_fmt bgr8 -i - -s 640x480 foo.avi</pre> <p>Sadly, I can't get the ffmpeg magic incantation quite right and it fails with</p> <pre> libavutil 50.15. 1 / 50.15. 1 libavcodec 52.72. 2 / 52.72. 2 libavformat 52.64. 2 / 52.64. 2 libavdevice 52. 2. 0 / 52. 2. 0 libavfilter 1.19. 0 / 1.19. 0 libswscale 0.11. 0 / 0.11. 0 libpostproc 51. 2. 0 / 51. 2. 0 Output #0, avi, to 'out.avi': Stream #0.0: Video: flv, yuv420p, 640x480, q=2-31, 19660 kb/s, 90k tbn, 30 tbc [image2pipe @ 0x1508640]max_analyze_duration reached [image2pipe @ 0x1508640]Estimating duration from bitrate, this may be inaccurate Input #0, image2pipe, from 'pipe:': Duration: N/A, bitrate: N/A Stream #0.0: Video: 0x0000, bgr8, 25 fps, 25 tbr, 25 tbn, 25 tbc swScaler: 0x0 -> 640x480 is invalid scaling dimension </pre> <ul> <li>The captured frames are definitely 640x480.</li> <li>I'm pretty sure the pixel order for the OpenCV image type (IplImage) is GBR, one byte per channel. At least, that's what seems to be coming off the camera.</li> </ul> <p>I'm no ffmpeg guru. Has anyone done this successfully?</p>

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