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• `ffmpet -f concat` don't work when all input streams appear to have the same spec

  9 mars 2023, par Roy

  My ffmpeg command :

  


  ffmpeg -safe 0 -f concat -i list.txt -c copy out.mp4


  


  My 1st input file :

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\Applications\ffmpeg_6.0_full\a.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.3.100
  Duration: 00:00:04.97, start: 0.000000, bitrate: 40 kb/s
  Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 2 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 27 kb/s, 30 fps, 30 tbr, 30k tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc60.3.100 libx264


  


  My 2nd input file :

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\Applications\ffmpeg_6.0_full\b.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp41isom
    creation_time   : 2023-03-08T06:47:13.000000Z
    artist          : Microsoft Game DVR
    title           : PUBG: BATTLEGROUNDS
  Duration: 00:10:00.16, start: 0.000000, bitrate: 20885 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 20739 kb/s, 30 fps, 30 tbr, 30k tbn (default)
    Metadata:
      creation_time   : 2023-03-08T06:47:13.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : AVC Coding
  Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 131 kb/s (default)
    Metadata:
      creation_time   : 2023-03-08T06:47:13.000000Z
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]


  


  The above command outputs some warning signals :

  


  [mov,mp4,m4a,3gp,3g2,mj2 @ 0000025239902d40] Auto-inserting h264_mp4toannexb bitstream filter
[mp4 @ 00000252396fe5c0] Non-monotonous DTS in output stream 0:1; previous: 218112, current: 150024; changing to 218113. This may result in incorrect timestamps in the output file.
...
a lot of them
...
frame=25992 fps=21754 q=-1.0 Lsize= 1519621kB time=00:14:49.39 bitrate=13996.8kbits/s speed= 744x
video:9649kB audio:1519216kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


  


  The resultant video can play the first part of the video correctly, then the video players either skips directly to the end of the video (MPC-HC), or don't render anything at all while timer passes as normal (VLC).

  


  My impression of the concat is that it requires all videos to have the same spec, which I think my input achieved (all the "Steam #0:0", etc, line matches). I only see the following difference, which I assumed that should be okay :

  


  

  1. Metadata are different both for the whole input (e.g. "major_brand") and for each stream (e.g. "encoder"). I assumed that metadata won't affect the processing.

  


  2. The order of video/audio streams are different in the two inputs : the 1st input file has audio then video ; the 2nd input file has video then audio. I assumed that ffmpeg knows the difference and won't concat a video stream to an audio stream.

  


  


  The full output of the command can be found in this pastebin : https://pastebin.com/Z5q97Uyg

  


• Audio Files downloaded from YouTube-DL are corrupted

  1er juin 2022, par Sushil

  I have written a small piece of code that downloads audios and videos from YouTube using YouTube-DL. Here is my code :

  


  from __future__ import unicode_literals
import youtube_dl

link = input("Enter the video link:")

while True:
    choice = input("Enter a for audio file, v for video file:")
    if choice == "a" or choice == "v":
        break

ydl_opts = {}

if choice == "a":
    ydl_opts = {
        'format': 'bestaudio/best',
        'postprocessors': [{
            'key': 'FFmpegExtractAudio',
            'preferredcodec': 'mp3',
            'preferredquality': '192',
        }],
    }
else:
    ydl_opts = {'format':137}
    
with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    info_dict = ydl.extract_info(link, download=False)
    video_title = info_dict.get('title', None)

if choice == "a":
    path = f'D:\\DwnldsYT\\{video_title}.mp3'
if choice == "v":
    path = f'D:\\DwnldsYT\\{video_title}.mp4'

ydl_opts.update({'outtmpl':path})

with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download([link])


  


  This works fine. I am able to play the downloaded audio. But when I try to read the same audio file, it shows me an error.

  


  Code :

  


  from pydub import AudioSegment

song = AudioSegment.from_mp3("D:\\DwnldsYT\\Cartoon - On & On (feat. Daniel Levi) [NCS Release].mp3")


  


  Output :

  


  Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[mp3float @ 000001f2425c2500] Header missing
Error while decoding stream #0:0: Invalid data found when processing input
[abuffer @ 000001f242280300] Value inf for parameter 'time_base' out of range [0 - 2.14748e+09]
    Last message repeated 3 times
[abuffer @ 000001f242280300] Error setting option time_base to value 1/0.
[graph_0_in_0_0 @ 000001f242280e80] Error applying options to the filter.
Error reinitializing filters!
Error while filtering: Result too large
Finishing stream 0:0 without any data written to it.
[abuffer @ 000001f242280300] Value inf for parameter 'time_base' out of range [0 - 2.14748e+09]
    Last message repeated 3 times
[abuffer @ 000001f242280300] Error setting option time_base to value 1/0.
[graph_0_in_0_0 @ 000001f242280e80] Error applying options to the filter.
Error configuring filter graph
Conversion failed!


  


  Is this because the audio downloaded is corrupted ? And how to solve this problem ? Any help would be appreciated. Thanks !

  


• WebRTC books – a brief review

  1er janvier 2014, par silvia

  I just finished reading Rob Manson’s awesome book “Getting Started with WebRTC” and I can highly recommend it for any Web developer who is interested in WebRTC.

  Rob explains very clearly how to create your first video, audio or data peer-connection using WebRTC in current Google Chrome or Firefox (I think it also now applies to Opera, though that wasn’t the case when his book was published). He makes available example code, so you can replicate it in your own Web application easily, including the setup of a signalling server. He also points out that you need a ICE (STUN/TURN) server to punch through firewalls and gives recommendations for what software is available, but stops short of explaining how to set them up.

  Rob’s focus is very much on the features required in a typical Web application :

  • video calls
  • audio calls
  • text chats
  • file sharing

  In fact, he provides the most in-depth demo of how to set up a good file sharing interface I have come across.

  Rob then also extends his introduction to WebRTC to two key application areas : education and team communication. His recommendations are spot on and required reading for anyone developing applications in these spaces.

  —

  Before Rob’s book, I have also read Alan Johnson and Dan Burnett’s “WebRTC” book on APIs and RTCWEB protocols of the HTML5 Real-Time Web.

  Alan and Dan’s book was written more than a year ago and explains that state of standardisation at that time. It’s probably a little out-dated now, but it still gives you good foundations on why some decisions were made the way they are and what are contentious issues (some of which still remain). If you really want to understand what happens behind the scenes when you call certain functions in the WebRTC APIs of browsers, then this is for you.

  Alan and Dan’s book explains in more details than Rob’s book how IP addresses of communication partners are found, how firewall holepunching works, how sessions get negotiated, and how the standards process works. It’s probably less useful to a Web developer who just wants to implement video call functionality into their Web application, though if something goes wrong you may find yourself digging into the details of SDP, SRTP, DTLS, and other cryptic abbreviations of protocols that all need to work together to get a WebRTC call working.

  —

  Overall, both books are worthwhile and cover different aspects of WebRTC that you will stumble across if you are directly dealing with WebRTC code.