Using environment variable to store capture options by adamrankin · Pull Request #9292 · opencv/opencv

adamrankin · 2017-08-01T20:42:32Z

String is parsed by av_dict_parse_string(ENV{OPENCV_FFMPEG_CAPTURE_OPTIONS}, ";", "|")

resolves #9290

This pullrequest changes

Allows configuration of ffmpeg capture options via environment variable. If variable is not set or OpenCV cannot read env variables, defaults to TCP as per previous behaviour.

…tring(ENV{OPENCV_FFMPEG_CAPTURE_OPTIONS}, ";", "|")

adamrankin · 2017-08-01T21:47:53Z

Hello, I'm having trouble identifying which version of ffmpeg is used for the build. I set up a linux build of FFMPEG/OpenCV and I don't get any compile issues.

Any help would be appreciated.

berak · 2017-08-02T04:31:54Z

from here (quite at the bottom), that's the failed one:

--   Video I/O:
--     DC1394 1.x:                  NO
--     DC1394 2.x:                  NO
--     FFMPEG:                      YES
--       avcodec:                   YES (ver 54.35.1)
--       avformat:                  YES (ver 54.20.4)
--       avutil:                    YES (ver 52.3.0)
--       swscale:                   YES (ver 2.1.1)
--       avresample:                NO
--     GStreamer:                   NO

while the linux opencl bot (success) has:

--     FFMPEG:                      YES
--       avcodec:                   YES (ver 56.60.100)
--       avformat:                  YES (ver 56.40.101)
--       avutil:                    YES (ver 54.31.100)
--       swscale:                   YES (ver 3.1.101)
--       avresample:                NO

alalek · 2017-08-02T09:03:29Z

These builders are based on Ubuntu 14.04 (failed) and Ubuntu 16.04 (passed).
You need to determine related API changes from ffmpeg and libav and specify proper "#ifdef" guards to use av_dict_parse_string.

alalek · 2017-08-02T15:21:25Z

modules/videoio/src/cap_ffmpeg_impl.hpp

 #endif

-#if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(52, 111, 0)
+#if LIBAVFORMAT_BUILD > CALC_FFMPEG_VERSION(51,11,0)


Why is this change here?

Condition must be ">=". ">" should not be used at all for version checks.

Perhaps we should check for 53.4.0 (avformat_open_input)

These change must be propagated to many places with "dict" (av_dict_free / declaration / etc)

Ah crap, this is a mistake. Sorry about the sloppy commits.

With regards to 53.4.0, that makes sense to me. However, I am already making mistakes with regards to ffmpeg version checks, so ideally I would make as few changes as possible.

alalek · 2017-08-02T15:24:17Z

modules/videoio/src/cap_ffmpeg_impl.hpp

+    }
+    else
+    {
+#if LIBAVUTIL_BUILD > CALC_FFMPEG_VERSION(52,6,0)


"lavu 52.17.100 / 52.7.0"

#if LIBAVUTIL_BUILD >= (LIBAVUTIL_VERSION_MICRO >= 100 ? CALC_FFMPEG_VERSION(52, 17, 100) : CALC_FFMPEG_VERSION(52, 7, 0))

Thanks, I am unfamiliar with the ffmpeg versioning. Fixes incoming.

Copy/paste error due to coder mistake reverted Proper version checking for LIBAVUTIL_BUILD

adamrankin · 2017-08-02T16:08:07Z

New code usage could be as follows:

#if WIN32
  _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", "rtsp_transport;udp");
#else
  setenv("OPENCV_FFMPEG_CAPTURE_OPTIONS", "rtsp_transport;udp");
#endif

auto capture = cv::VideoCapture(someURL, cv::CAP_FFMPEG);

#if WIN32
  _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", "");
#else
  unsetenv("OPENCV_FFMPEG_CAPTURE_OPTIONS");
#endif

PhilLab · 2017-08-07T16:03:54Z

Definitely interesting, thanks a lot 👍
Was the old idea of using an enum not applicable for this patch? I.e. an enum CV_FFMPEG_CAP_TRANSPORT_UDP which can be set to 0.0 or 1.0.

And is there a place in the documentation where your latest comment could be added?

adamrankin · 2017-08-07T16:12:10Z

Hmm, that does seem cleaner. The only pro to this method (I was inspired by another bug report of a similar topic) is that now you can pass any option(s) to ffmpeg.

I'm happy to write it up, but I'm not familiar with the docs. I'd appreciate any pointer to the right spot!

PhilLab · 2017-08-07T16:22:33Z

Both ways have their pros/cons. I'm unsure which one to prefer.
Regarding the enum way, I would place it like the device-specific flags which are documented by //!< (cf. the videoio.hpp)

adamrankin · 2017-08-31T20:02:11Z

I think I would stay with the current implementation. Is this mergeable?

vpisarev · 2017-09-13T14:26:40Z

how robust is the solution? Assume that there are 2 apps on a system, one just uses opencv + ffmpeg to read videos from disk, another one reads videos via network and so the options are relevant. This solution is global and so the first app will stop working. Shall we come up with some better solution?

adamrankin · 2017-09-13T14:39:31Z

@vpisarev I'm open to other solutions, but this solution is only global if the env variable is set permanently. Given my code example above, the options can be set in the code (more advanced code could cache any pre-existing options, and then restore them after connecting) without applying to other programs.

alalek · 2017-09-13T18:04:45Z

Environment variables have process scope, so solution/workaround is fine until we have some configuration API in OpenCV.
Looks good to me 👍

* Using environment variable to store options parsed by av_dict_parse_string(ENV{OPENCV_FFMPEG_CAPTURE_OPTIONS}, ";", "|") * Adding missing mandatory flags parameter * Guarding against missing function via LIBAVUTIL version * Code review fixes Copy/paste error due to coder mistake reverted Proper version checking for LIBAVUTIL_BUILD

golden0080 · 2017-11-20T22:37:42Z

Hey, Guys, I'm happy to find out that TCP issue is fixed in this patch. But only by reading code, I'm a little bit confused how to tell OpenCV to use UDP whenever reading RTSP streams. Can you guys kindly provide a simple example?

adamrankin · 2017-11-20T22:50:58Z

You'll have to set an environment variable when creating the device

#if WIN32
  _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", "rtsp_transport;udp");
#else
  setenv("OPENCV_FFMPEG_CAPTURE_OPTIONS", "rtsp_transport;udp");
#endif

auto capture = cv::VideoCapture(someURL, cv::CAP_FFMPEG);

#if WIN32
  _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", "");
#else
  unsetenv("OPENCV_FFMPEG_CAPTURE_OPTIONS");
#endif

think-free · 2019-01-24T14:34:18Z

This solution doesn't work on windows when using a dynamic library. Something like this seems to occure.
Ffmpeg parameters should be passed as parameters or configured by calling a function before the open.

The use case is when mixing several rtsp stream with mixed protocol (udp,tcp) in the same executable. The environment variable set by code isn't reflected in the opencv library.

Works fine on linux ...

adamrankin · 2019-01-24T16:40:09Z

What a pain, thank you for catching this. I recommend opening a new issue to change the env var approach!

osmantoker · 2020-03-29T17:55:13Z

You'll have to set an environment variable when creating the device

#if WIN32
  _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", "rtsp_transport;udp");
#else
  setenv("OPENCV_FFMPEG_CAPTURE_OPTIONS", "rtsp_transport;udp");
#endif

auto capture = cv::VideoCapture(someURL, cv::CAP_FFMPEG);

#if WIN32
  _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", "");
#else
  unsetenv("OPENCV_FFMPEG_CAPTURE_OPTIONS");
#endif

hi, how can I set this env. on Java OpenCV?

adamrankin added 2 commits August 1, 2017 16:40

Using environment variable to store options parsed by av_dict_parse_s…

ec502a9

…tring(ENV{OPENCV_FFMPEG_CAPTURE_OPTIONS}, ";", "|")

Adding missing mandatory flags parameter

f0e7868

Guarding against missing function via LIBAVUTIL version

01c1971

alalek reviewed Aug 2, 2017

View reviewed changes

Code review fixes

1eca80b

Copy/paste error due to coder mistake reverted Proper version checking for LIBAVUTIL_BUILD

vpisarev self-assigned this Sep 13, 2017

vpisarev removed their assignment Sep 19, 2017

vpisarev merged commit fb8143d into opencv:master Sep 19, 2017

alalek mentioned this pull request Oct 9, 2017

ffmpeg: update 3.3.4 #9805

Merged

adamrankin deleted the ffmpeg_capture_options branch December 11, 2017 02:08

adamrankin mentioned this pull request Jan 19, 2018

BUG: Reverting hardcoded TCP hack for RTSP streaming via ffmpeg #9291

Closed

alalek mentioned this pull request Dec 4, 2019

Support custom options in AVCodecContext (av_dict_set) in FFMPEG backend #6342

Open

pletessier mentioned this pull request Jan 6, 2020

Videocapture skip frames #16190

Merged

OrriMandarin mentioned this pull request Aug 29, 2020

Can not read camera rtsp #17734

Closed

1 task

alalek mentioned this pull request Feb 23, 2021

videoio: HW decode/encode in FFMPEG backend; new properties with support in FFMPEG/GST/MSMF #19460

Merged

6 tasks

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