Recherche avancée

Sur d’autres sites (4885)

• Revision e707e9580b : libs.mk : don't include x86inc.asm in codec src list this file is an include and

  28 juin 2014, par James Zern

  Changed Paths :
   Modify /libs.mk

  
  
  libs.mk : don’t include x86inc.asm in codec src list

  this file is an include and doesn’t need to be built on its own.
  fixes :
  ranlib : file : libvpx_g.a(x86inc.asm.o) has no symbols

  Change-Id : I89504e37ff0a4488489af7b9b7e09fb32acc4853

• avformat/mov : move edit list heuristics into mov_build_index()

  12 novembre 2014, par Clément Bœsch

  avformat/mov : move edit list heuristics into mov_build_index()
  mov_read_elst() is now only responsible from storing the table in a data
  
  structure ; this is consistent with other table readers functions.
  

  • [DH] libavformat/isom.h
  • [DH] libavformat/mov.c

• How to build list of tasks for asyncio.gather in Python 3.8

  22 juillet 2020, par mcgregor94086

  Below I have attached a test program to demonstrate a problem I am having with asyncio.gather throwing a TypeError.

  


  My objective : To make multiple concurrent asynchronous calls to capture camera images to files from an array of USB cameras attached to my computer. When all cameras have completed their async captures, I want then resume processing.

  


  The async coroutine take_image() shown here makes a system call to the "ffmpeg" application that captures an image from the specified camera to a specified file.

  


  import asyncio
import os
import subprocess
import time

async def take_image(camera_id, camera_name, image_file_path, image_counter):
    image_capture_tic = time.perf_counter()
    try:
        run_cmd = subprocess.run( ["ffmpeg", '-y', '-hide_banner', '-f', 'avfoundation', '-i', camera_id,
                                   '-frames:v', '1', '-f', 'image2', image_file_path], universal_newlines=True,
                                 stdout=subprocess.PIPE, stderr=subprocess.PIPE)  # Note, ffmpeg writes to stderr, not stdout!
    except Exception as e:
        print("Error: Unable to capture image for", image_file_path)
        return "NO IMAGE!"

    image_capture_toc = time.perf_counter()
    print(f"{image_counter}: Captured {camera_name} image in: {image_capture_toc - image_capture_tic:0.0f} seconds")
    return camera_name


  


  The main() routine shown below takes a list of multiple cameras, and iterating over each camera in the list, main() makes creates an asyncio task for each camera using asyncio.create_task(). Each task is added to a list of tasks.

  


  Once all image capture tasks have been started, I await their completion using await asyncio.gather(tasks).

  


  async def main():
    tic = time.perf_counter()
    camera_list = [('0', 'FHD Camera #1'),  ('1', 'FHD Camera #2'), ('2', 'FHD Camera #3'), ]
    image_counter = 1
    tasks = []
    for camera_pair in camera_list:
        camera_id, camera_name = camera_pair
        image_file_name = 'img' + str(image_counter) + "-cam" + str(camera_id)  + "-" + camera_name + '.jpg'
        image_file_path = os.path.join("/tmp/test1/img", image_file_name)

        # schedule all image captures calls *concurrently*:
        tasks.append(asyncio.create_task(take_image(camera_id, camera_name, image_file_path, image_counter),
                     name=image_file_name))
        image_counter = image_counter + 1

    await asyncio.gather(tasks) # <-- This line throws a TypeError!
    toc = time.perf_counter()
    print(f"Captured list of {image_counter - 1} cameras in: {toc - tic:0.0f} seconds")

asyncio.run(main())


  


  Unfortunately, when I attempt to run this program, I am getting this error :

  


  TypeError : unhashable type : 'list'

  


  and the following Traceback :

  


  Traceback (most recent call last):&#xA;  File "scratch_10.py", line 41, in <module>&#xA;    asyncio.run(main())&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/runners.py", line 43, in run&#xA;    return loop.run_until_complete(main)&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/base_events.py", line 608, in run_until_complete&#xA;    return future.result()&#xA;  File "scratch_10.py", line 36, in main&#xA;    await asyncio.gather(tasks)&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/tasks.py", line 805, in gather&#xA;    if arg not in arg_to_fut:&#xA;TypeError: unhashable type: &#x27;list&#x27;&#xA;</module>

  


  I have been trying to puzzle through the 3.8 documentation on asyncio, but I don't understand what is wrong.

  


  How can I have each take_image request run asynchronously, and then resume processing in my calling routine once each task is complete ?