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• Video recorded from a webcam using FFmpeg is desynchronizing in iOS native player

  11 mars 2021, par Luuudo

  Objective

  


  I am trying to record a video (duration ≈ 1min to 4hours) from a webcam plugged into a PC. Then play just after the end of the recording the video on an Ipad connected to the same network as the PC.

  


  To do this I'm trying to record the video using ffmpeg (the detailed command I use is below). Then I serve the video that's on the PC to the Ipad via a Java server (The server works well with other videos so I don't think the problem is here).

  


  Problem

  


  When I play the video on the IPad native player, for example in Safari, the sound is going faster than the video and therefore it's desynchronizing from the video. If I request a certain time the video and audio re-sync then the audio is desynchronizing again while playing.

  


  

  • The video when played on VLC on the PC or on Firefox by requesting the server is well synced.

  


  • Another video (I downloaded this one to test) played on the Ipad from the server stay synced.

  


  


  It is only with the combination of a video record by myself using FFmpeg played in the iOS native player that I can observe the desynchronization.

  


  FFmpeg command

  


  I use FFmpeg to record the video from the webcam and save it into a file format readable on iOS.

  


  ffmpeg -y -f avfoundation -framerate 25 -pixel_format nv12 -video_size 1280x720 -i "0:0" -r 25 out.mp4


  


  The resulting recorded file info according to ffmpeg is below :

  


  > ffmpeg -i out.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:00:33.76, start: 0.000000, bitrate: 1510 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 1440 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 61 kb/s (default)
    Metadata:
      handler_name    : SoundHandler


  


  Compatible video formats from TV and Video iPad Pro specs

  


  


  Video formats supported : H.264 video up to 4K, 30 frames per second, High Profile level 4.2 with AAC‑LC audio up to 160 Kbps, 48kHz, stereo audio or Dolby Audio up to 1008 Kbps, 48kHz, stereo or multichannel audio, in .m4v, .mp4, and .mov file formats ; MPEG‑4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC‑LC audio up to 160 Kbps per channel, 48kHz, stereo audio or Dolby Audio up to 1008 Kbps, 48kHz, stereo or multichannel audio, in .m4v, .mp4, and .mov file formats ; Motion JPEG (M‑JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, audio in ulaw, PCM stereo audio in .avi file format

  


  


  I don't see what codecs or profiles I don't respect ?

  


  ps : I write PC but I'm currently trying this on a Mac. Eventually, I want to be able to do it also on Linux or even Windows. It looks like I just have to change the input devices to do that, which is avfoundation for MacOS.

  


• webm to mp4 without loosing audio video sync

  9 avril 2018, par Kishore

  Iam trying to covert webm to mp4 using ffmpeg so that the output file is playable in all browsers.

  Iam using this ffmpeg command in ubuntu

  ffmpeg -i inpput.webm -f mp4 -copyts -vcodec libx264 -strict -2 -vf scale="380:-2" -pix_fmt yuv420p -profile:v baseline -level 3 output.mp4 

  It is converting the file to mp4 but that file is out of sync in Mac safari browser and chrome browser. Means the audio and video is not syncing and sometimes the video gets stopped in between and audio goes on.

  If I play the input.web media file directly in chrome it is playing perfectly fine, the same input.webm is also playing good with firefox. But the converted mp4 is out of sync in safari on mac and all chrome browsers.

  However if the output.mp4 is played on ipad safari it is playing fine.
  The Mac safari version I tried is 11.03
  iPad safari version is 11.3

  Firefox and chrome are all latest.

  firefox : 59.0.2(64 bit),
  chrome : 65.0.3325.181 (Official Build) (64-bit)

  Please help me out with what Iam doing wrong.

  Thanks in advance.

• FFMPEG realtime streaming using a remote m3u8

  8 avril 2016, par JJ The Second

  Good morning chaps,

  I’ve been doing a long term research to do DRM solution for my client and we are almost there, here is what we’d like to achieve and please accept my lack of understanding, Im well new to FFMPEG and there are so many questions already asked but I’m not sure if they cover my questions.

  Objectives :

  1- To record and stream (real-time) m3u8 from a remote server : We have access to more than 3000 HLS streams (b2b project) therefore we would need to record and stream m3u8 in real-time. Currently I am able to record to mp4 or mkv but don’t understand how to stream real time

  2- Stream using HL264 : We would need to make sure streams play on all devices, based on my understanding this is the correct format to use, is this correct, more than happy to hear your comments

  3- Delivery to be in 3 different resolutions, HD, 488 and 380 : This is all about sizes, it is unlikely that my users would stream using mobile devices (GA says only 32000 using mobile) but still I need to make sure there are no restrictions to users

  Questions :

  1- I’ve seen lots of tutorials with regards to recording m3u8, converting to mp4 or .ts files, so I’m not sure how this works, do I need to export my recording to .ts files and merge them again ? If this is the case, isn’t this going to have delay in streaming ?

  2- By doing this, am I using my bandwidth or source of m3u8 ?

  3- If converting to .ts then would you please let me know how I can achieve this ?

  Please note, my recording are (for now) all m3u8 and I need to stream as m3u8 at the same time.

  I have latest version of FFMPEG installed on Ubuntu 14.4 TLS

  Thank you all in advance and happy Friday !