I am pulling my hair for a few days and I’m out of ideas.
I have two rtmp streams
- first stream is transcoded directly by myself (I use ffmpeg to transcode) and then I attach to that stream with opencv - VideoCapture can open the stream with no problem
- second stream is transcoded by 3rd party system (this system captures video through WebRTC and then encodes to h264) - this stream cannot be opened by VideCapture no matter what I do
I can attach with pure ffmpeg to that dodgy stream and I can restream - but this is not ideal as introduces extra network traffic and latency.
I was playing with OPENCV_FFMPEG_CAPTURE_OPTIONS environmental variable (I was trying to remove audio stream, change the video codec, playing with rtmp options) - no joy
So I figured I am trying to solve this problem from wrong end. I should somehow collect underlying ffmpeg logs that should be available when calling VideoCapture. So I tried to set OPENCV_FFMPEG_CAPTURE_OPTIONS="v;debug" but I can see no ffmpeg output when calling VideoCapture.
This is very simple python3 script I was using during tests:
import cv2 as cv
dodgy_cap = cv.VideoCapture()
dodgy_cap.open('rtmp://my_local_ip_address/rtmp/dodgy_stream_name')
print(dodgy_cap.isOpened()) # always returns False
healthy_cap = cv.VideoCapture()
healthy_cap.open('rtmp://my_local_ip_address/rtmp/healthy_stream_name')
print(healthy_cap.isOpened()) # always returns True
I collected information about both streams with ffprobe, but even though they look different I cannot see what would be the difference that prevents opencv from opening VideoCapture for dodgy stream…
This is a fragment from (very) verbose log for healthy stream:
RTMP_ClientPacket, received: notify 254 bytes
(object begin)
Property: <Name: no-name., STRING: onMetaData>
Property: <Name: no-name., ECMA_ARRAY>
(object begin)
Property: <Name: duration, NUMBER: 0.00>
Property: <Name: width, NUMBER: 2048.00>
Property: <Name: height, NUMBER: 1536.00>
Property: <Name: videodatarate, NUMBER: 0.00>
Property: <Name: framerate, NUMBER: 6.00>
Property: <Name: videocodecid, NUMBER: 7.00>
Property: <Name: title, STRING: Session streamed by "preview">
Property: <Name: comment, STRING: h264Preview_01_main>
Property: <Name: encoder, STRING: Lavf58.20.100>
Property: <Name: filesize, NUMBER: 0.00>
(object end)
(object end)
Metadata:
duration 0.00
width 2048.00
height 1536.00
videodatarate 0.00
framerate 6.00
videocodecid 7.00
title Session streamed by "preview"
comment h264Preview_01_main
encoder Lavf58.20.100
filesize 0.00
(... raw network packets ...)
Input #0, flv, from 'rtmp://my_local_ip_address/rtmp/healthy_stream_name':
Metadata:
title : Session streamed by "preview"
comment : h264Preview_01_main
encoder : Lavf58.20.100
Duration: 00:00:00.00, start: 159.743000, bitrate: N/A
Stream #0:0, 41, 1/1000: Video: h264 (High), 1 reference frame, yuv420p(progressive), 2048x1536, 0/1, 6 fps, 6 tbr, 1k tbn
And this is the fragment for dodgy stream:
RTMP_ClientPacket, received: notify 205 bytes
(object begin)
Property: <Name: no-name., OBJECT>
(object begin)
Property: <Name: metadatacreator, STRING: Agora.io SDK>
Property: <Name: encoder, STRING: Agora.io Encoder>
Property: <Name: audiocodecid, NUMBER: 10.00>
Property: <Name: audiosamplesize, NUMBER: 16.00>
Property: <Name: stereo, BOOLEAN: FALSE>
Property: <Name: audiosamplerate, NUMBER: 48000.00>
Property: <Name: videocodecid, NUMBER: 7.00>
Property: <Name: width, NUMBER: 640.00>
Property: <Name: height, NUMBER: 480.00>
(object end)
(object end)
RTMP_ReadPacket: fd=3
(... raw network packets ...)
Input #0, flv, from 'rtmp://my_local_ip_address/rtmp/dodgy_stream_name':
Duration: N/A, start: 4511.449000, bitrate: N/A
Stream #0:0, 41, 1/1000: Video: h264 (High), 1 reference frame, yuv420p(progressive, left), 640x480, 0/1, 15.17 fps, 15.08 tbr, 1k tbn, 30 tbc
Stream #0:1, 124, 1/1000: Audio: aac (LC), 48000 Hz, mono, fltp
Both streams don’t require any authentication (they are not exposed to the outside world)
I have no more ideas how can I debug this problem, please help…