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• message "avcodec_decode_video2 is deprecated" when trying to build h264_image_transport package in ROS

  14 septembre 2021, par Hugh Rivers

  I'm using a tello_driver for ROS and currently I am at a point where I want to subscribe to the transported images of the /tello/imag/raw/h264 topic in order to apply computer vision algorithms on the images in the next step.

  


  But I get the following warnings, when I try to build the h264_image_transport package inside the catkin workspace :

  


  [ 80%] Built target tello_driver_generate_messages_nodejs
[ 90%] Built target tello_driver_generate_messages_py
[ 90%] Built target tello_driver_generate_messages
/home/usr/catkin_ws/src/h264_image_transport/src/h264_subscriber.cpp: In member function ‘virtual void h264_image_transport::H264Subscriber::internalCallback(const ConstPtr&, const Callback&)’:
/home/usr/catkin_ws/src/h264_image_transport/src/h264_subscriber.cpp:47:69: warning: ‘int avcodec_decode_video2(AVCodecContext*, AVFrame*, int*, const AVPacket*)’ is deprecated [-Wdeprecated-declarations]
   47 |     int len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
      |                                                                     ^
In file included from /home/usr/catkin_ws/src/h264_image_transport/include/h264_image_transport/h264_subscriber.h:14,
                 from /home/usr/catkin_ws/src/h264_image_transport/src/h264_subscriber.cpp:3:
/usr/include/x86_64-linux-gnu/libavcodec/avcodec.h:4828:5: note: declared here
 4828 | int avcodec_decode_video2(AVCodecContext *avctx, AVFrame *picture,
      |     ^~~~~~~~~~~~~~~~~~~~~
/home/usr/catkin_ws/src/h264_image_transport/src/h264_subscriber.cpp:47:69: warning: ‘int avcodec_decode_video2(AVCodecContext*, AVFrame*, int*, const AVPacket*)’ is deprecated [-Wdeprecated-declarations]
   47 |     int len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
      |                                                                     ^
In file included from /home/usr/catkin_ws/src/h264_image_transport/include/h264_image_transport/h264_subscriber.h:14,
                 from /home/usr/catkin_ws/src/h264_image_transport/src/h264_subscriber.cpp:3:
/usr/include/x86_64-linux-gnu/libavcodec/avcodec.h:4828:5: note: declared here
 4828 | int avcodec_decode_video2(AVCodecContext *avctx, AVFrame *picture,
      |     ^~~~~~~~~~~~~~~~~~~~~
[ 95%] Linking CXX shared library /home/usr/catkin_ws/devel/lib/libh264_image_transport.so
[100%] Built target h264_image_transport


  


  Basically, the message tells me that avcodec_decode_video2 is deprecated. When I did some research I found that avcodec_send_packet() and avcodec_receive_frame() can be used instead but I have unfortunately no idea how to do that. Could someone help me here please, or is there another way to fix that ? Thanks !

  


• python imageio.get_reader() returns format error

  19 août 2020, par tristan_jia

  import imageio

reader = imageio.get_reader("./t.mp4")


  


  As shown above, with python 3.6.10, it returns :

  


  >>> reader = imageio.get_reader("../")&#xA;Traceback (most recent call last):&#xA;  File "<stdin>", line 1, in <module>&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/core/functions.py", line 129, in get_reader&#xA;    return format.get_reader(request)&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/core/format.py", line 168, in get_reader&#xA;    return self.Reader(self, request)&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/core/format.py", line 217, in __init__&#xA;    self._open(**self.request.kwargs.copy())&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/plugins/ffmpeg.py", line 357, in _open&#xA;    self._initialize()&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/plugins/ffmpeg.py", line 430, in _initialize&#xA;    shell=ISWIN)&#xA;  File "/usr/lib64/python3.6/subprocess.py", line 729, in __init__&#xA;    restore_signals, start_new_session)&#xA;  File "/usr/lib64/python3.6/subprocess.py", line 1364, in _execute_child&#xA;    raise child_exception_type(errno_num, err_msg, err_filename)&#xA;OSError: [Errno 8] Exec format error: &#x27;/home/tristan_jia/.imageio/ffmpeg/ffmpeg-linux64-v3.3.1&#x27;&#xA;&#xA;</module></stdin>

  


  I searched everywhere but haven't seen any similar questions. The script runs on Opensuse Leap 15.1, is it related to the system I use ?

  


• Implementing '-async 1' in C code to correct out of sync audio

  25 septembre 2013, par Christian P.

  I have built a segmenter that takes as input a h264 / AAC video and segments according to the HLS specification. The source code for it can be seen here : https://gist.github.com/cpnielsen/f36729c371aac0fe535d

  It is implemented as a python extension, but the interesting parts are in the process_video() function. It makes use of the libav library (alternatively ffmpeg) to do the heavy lifting.

  It works 95% of the time, but we have come upon some videos where it produces segments with audio out of sync. If I was using the command-line tool, I could simply add -async 1 to fix it, but how do I implement the same functionality in my C code ?

  I found a snippet of code in avconv_filter.c (for libav, not sure what the ffmpeg equivalent is) where they initiate the filter, but without any documentation it is hard to figure out how to do this outside the whole modular setup.

  I just need to :

  1. Initiate the correct filter
  2. Apply it to the input (or output ? not sure)
  3. Know of any pitfalls when using the filter.

  Any help is welcome ; sample code, explanation of the filter, etc.