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• FFMPEG command error : audio device not found

  29 mai 2024, par Yash Rajput

  So, basically i am making a google meet audio recorder (bot) and i wanna automate the audio recording process as soon as i enters into the meet. but my the code is not working as expected.

  


  I'm using the FFMPEG to record the audio and save it to the local machine at the desired location but it's throwing the error as shown in the picture.Error that i am getting

  


  I am using the correct name of my audio input device but still it's showing the same error , there's only one input audio driver installed on my machine as you can see it in a picture.name of audio input device/driver

  


  the FFMPEG command that i am writing to record the audio in windows OS is : FFMPEG command

  


• Merge video with ffmpeg(or alternatives) with extra properties(an overlay)

  28 juin 2021, par dconixDev

  I'll be scraping clips from twitch and merging them to create a single video file.
I already figured out the scraping of twitch clip links(but i only get 16-20 videos because i need to scroll with selenium but i dont really mind it, if you have a working solution then make an answer about it) and also the simple merging videos.

  


  I'm scraping links with :

  


  #!/usr/bin/python3.9
import bs4
import requests
import time
from datetime import datetime
from selenium import webdriver
from selenium.webdriver.firefox.options import Options

# Initialize driver and run it headless
options = Options()
options.headless = True
driver = webdriver.Firefox(options=options)

def extract_source(url):
     agent = {"User-Agent":"Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Firefox/78.0"}
     source=requests.get(url, headers=agent).text
     return source

def extract_data(source):
     soup=bs4.BeautifulSoup(source, 'html.parser')
     names=soup.find_all('a', attrs={'data-a-target':'preview-card-image-link'})
     return names

driver.get('https://www.twitch.tv/directory/game/League%20of%20Legends/clips?range=24hr')

# I wait 3 seconds for the clips to get pulled in
# I'd like here to scroll down a bit so i can scrape more clips, but even after i tried some solutions my firefox(was debugging in GUI mode, not headless as it is now) wasnt scrolling
time.sleep(3)
extract_links=extract_data(driver.page_source)
for a in extract_links:
    print(a.get('href'))

driver.quit()

# I tried scrolling using this but didnt work, not sure why
# this script is supposed to scroll until youre at the end of the page
# SCROLL_PAUSE_TIME = 0.5

# # Get scroll height
# last_height = driver.execute_script("return document.body.scrollHeight")

# for i in range(3):
    # # Scroll down to bottom
    # driver.execute_script("window.scrollTo(0, document.body.scrollHeight);")

    # # Wait to load page
    # time.sleep(SCROLL_PAUSE_TIME)

    # # Calculate new scroll height and compare with last scroll height
    # new_height = driver.execute_script("return document.body.scrollHeight")
    # if new_height == last_height:
        # break
    # last_height = new_height


  


  I'm joining videos together after downloading(with youtube-dl) with ffmpeg :

  


  ffmpeg -safe 0 -f concat -segment_time_metadata 1 -i videos.txt -vf select=concatdec_select -af aselect=concatdec_select,aresample=async=1 out.mp4

  


  Where videos.txt is as follows :

  


  file 'video_file1.mp4'
file 'video_file2.mp4'
...


  


  I can't really find answers on how to add a watermark(different for each video, although i found this it doesnt explain how to add a unique watermark to individual videos but the same watermark to two videos) without having to render each and every video twice but doing so in one go.

  


  I think I stumbled upon some people who made their videos.txt as follows in purpose of adding extra options to each video :

  


  file 'video_file1.mp4'
option 1(for video_file1.mp4)
option 2(for video_file1.mp4)
file 'video_file2.mp4'
option 1(for video_file2.mp4)
option 2(for video_file2.mp4)
...


  


  Would this work for unique watermarks for each videos(lets suppose watermarks are named video_file1.png, ... meaning the same as the videos, also the watermark is transparent in case that needs more configuration)

  


• usb_fill_bulk_urb with less buffer_length gives no garbage Transport stream data

  4 février 2015, par user3570793

  Currently I am working on a DVB-T2 dongle which is connected to my Ubuntu laptop 14.04 using USB

  interface.

  I am using following applications to perform scanning and channel play.
  1. w_scan - which scans and gives me a channel.conf file
  2. vlc ./channel.conf - plays a channel using modulation parameters in channel.conf

  Things work fine when Pid filtering is disabled. But when Pid filtering is enabled, I see

  macroblocks on the screen instead of smooth AV. Even AV is breaking a lot.

  After going through the driver code, I tried increasing the URB buffer size from 3K (21*188) to

  64K (348*188). The AV became smooth.

  This urb buffer size is buffer_length (lenght of transport buffer) in below function.

  void usb_fill_bulk_urb (struct urb * urb, struct usb_device * dev,
  unsigned int pipe, void * transfer_buffer,
  int buffer_length, usb_complete_t complete_fn,
  void * context) ;

  As you can see the driver uses bulk mode of usb transfer.

  Could anyone explain me why increasing the buffer is solving the macroblock issue ?

  Give me some pointers to understand this issue better.

  Thanks in advance,
  Murali