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• How to record a webcam to a file outside of X11 ?

  13 décembre 2017, par Dav Clark

  I’m working with teachers to automatically record their classes, so we can review them and improve the quality of teaching. We have computers running Ubuntu 17.10 with multiple webcams in a couple of classrooms - but I could run other software if it makes this task easier.

  I can successfully record a stream from the webcam to an h264 encoded file using gstreamer. The following should work for most people with gstreamer installed, but I’ve got fancier pipelines using vaapi that can simultaneously encode multiple 4k streams on a NUC with room to spare ! My point is that Gstreamer works great when I’m typing at a terminal in the GUI. The example :

  .\gst-launch-1.0.exe -e autovideosrc ! videoconvert ! \
  
    openh264enc max-bitrate=256000 ! h264parse ! \
  
    mp4mux ! filesink location=somefile.mp4

  I imagine I could also do this with ffmpeg, or OpenCV, or maybe even VLC (I can record a webcam via the GUI, so I guess I could use that to generate a command line ?).

  But when I tried any of the above, for example, via SSH, I get errors from GStreamer and OpenCV, and blank videos from ffmpeg (I haven’t tried VLC because I don’t currently have access to these machines). I need to automate - but I could potentially leave a user logged in. I just need to have some way to capture webcam to disk with some amount of reasonable compression.

  I naively thought I could throw something like the above into a cron job and I’d be good to go (intending to send a SIGINT to end recording). But anything that can be automatically scheduled somehow would be great.

  EDIT : Below is an approach I’m trying using ffmpeg. You can see from the output that I can’t figure out how to specify pixel_format in a way that ffmpeg pays attention to ! First, the command (using mkv because that seems to be a "low-stress" format, but have also tried mov and mp4) :

  ffmpeg -hwaccel vaapi -vaapi_device /dev/dri/renderD128 \
  
    -f v4l2 -framerate 30 -video_size hd720 -pixel_format yuv420p -i /dev/video1 output.mkv

  Like I said, I’m trying to get hardware acceleration, and you can see below that VAAPI is working (but I think just for decoding). You can easily remove the options from the first line, and I get similar results either way. I didn’t include the header with compile options and library versions, as it’s standard Ubuntu 17.10.

  libva info: VA-API version 0.40.0
  
  libva info: va_getDriverName() returns 0
  
  libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/i965_drv_video.so
  
  libva info: Found init function __vaDriverInit_0_40
  
  libva info: va_openDriver() returns 0
  
  Input #0, video4linux2,v4l2, from '/dev/video1':
  
    Duration: N/A, start: 42437.238243, bitrate: 442368 kb/s
  
      Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1280x720, 442368 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
  
  File 'output.mkv' already exists. Overwrite ? [y/N] y
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
  Press [q] to stop, [?] for help
  
  No pixel format specified, yuv422p for H.264 encoding chosen.
  
  Use -pix_fmt yuv420p for compatibility with outdated media players.
  
  [libx264 @ 0x55d1a26a71a0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
  
  [libx264 @ 0x55d1a26a71a0] profile High 4:2:2, level 3.1, 4:2:2 8-bit
  
  [libx264 @ 0x55d1a26a71a0] 264 - core 148 r2795 aaa9aa8 - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, matroska, to 'output.mkv':
  
    Metadata:
  
      encoder         : Lavf57.71.100
  
      Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv422p, 1280x720, q=-1--1, 30 fps, 1k tbn, 30 tbc
  
      Metadata:
  
        encoder         : Lavc57.89.100 libx264
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
  
  Past duration 0.717049 too large
  
  Past duration 0.879128 too large
  
  frame=  567 fps= 16 q=27.0 size=    2156kB time=00:00:34.16 bitrate= 516.9kbits/s speed=0.938x

  I exit with ctrl-C. Which results in what appears to be an orderly exit :

  [libx264 @ 0x55d1a26a71a0] frame I:11    Avg QP:15.75  size: 18573
  
  [libx264 @ 0x55d1a26a71a0] frame P:2176  Avg QP:19.91  size:  4435
  
  [libx264 @ 0x55d1a26a71a0] frame B:173   Avg QP:20.00  size:  3232
  
  [libx264 @ 0x55d1a26a71a0] consecutive B-frames: 90.1%  0.1%  0.6%  9.2%
  
  [libx264 @ 0x55d1a26a71a0] mb I  I16..4: 34.0% 56.1%  9.8%
  
  [libx264 @ 0x55d1a26a71a0] mb P  I16..4:  0.1%  1.2%  0.0%  P16..4: 32.7%  3.1%  6.1%  0.0%  0.0%    skip:56.8%
  
  [libx264 @ 0x55d1a26a71a0] mb B  I16..4:  0.0%  0.3%  0.0%  B16..8: 31.9%  0.7%  0.1%  direct: 1.4%  skip:65.6%  L0:41.8% L1:57.9% BI: 0.3%
  
  [libx264 @ 0x55d1a26a71a0] 8x8 transform intra:81.2% inter:92.4%
  
  [libx264 @ 0x55d1a26a71a0] coded y,uvDC,uvAC intra: 25.4% 20.1% 2.1% inter: 10.2% 7.4% 0.0%
  
  [libx264 @ 0x55d1a26a71a0] i16 v,h,dc,p: 78% 10%  7%  5%
  
  [libx264 @ 0x55d1a26a71a0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  7%  6% 72%  2%  3%  3%  2%  2%  3%
  
  [libx264 @ 0x55d1a26a71a0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 34% 21% 25%  4%  5%  3%  4%  1%  3%
  
  [libx264 @ 0x55d1a26a71a0] i8c dc,h,v,p: 69% 14% 15%  2%
  
  [libx264 @ 0x55d1a26a71a0] Weighted P-Frames: Y:1.7% UV:0.1%
  
  [libx264 @ 0x55d1a26a71a0] ref P L0: 49.3%  2.7% 29.6% 18.1%  0.3%
  
  [libx264 @ 0x55d1a26a71a0] ref B L0: 69.3% 24.1%  6.6%
  
  [libx264 @ 0x55d1a26a71a0] ref B L1: 86.6% 13.4%
  
  [libx264 @ 0x55d1a26a71a0] kb/s:529.95
  
  Exiting normally, received signal 2.

• How to embed cover art into MP4 without errors ?

  7 mai 2020, par symonxd

  I want to add artwork to my MP4 file. How do I do this successfully / without errors ?
I've tried these methods with numerous MP4 files, none worked.
If you would like to replicate the errors / bugs, here are the sample files I've used for this question.

  



  I've tried the following :

  



  ---

  



  

  1. ffmpeg -i sample.mp4 -i sample.png -map 0 -map 1 -c copy -disposition:v:0 attached_pic sample_w_artwork.mp4
as stated by Lukas

  


  



  with this error :

  



  [mp4 @ 0000019ee4852280] Could not find tag for codec h264 in stream #0, codec not currently supported in container
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument


  



  ffmpeg 4.2.2 (Windows build by Zeranoe)

  



  

  2. atomicparsley sample.mp4 --artwork sample.png --overWrite

  


  



  with no success ; AtomicParsley

  



  I get this message when executing the first time :

  



  Started writing to temp file.
 Progress: =============================================>100%|
 Finished writing to temp file.


  



  Executing the next (nth) time gives this :

  



  Updating metadata...   completed.


  



  

  3. Adding artwork through the GUI Tag Editor using both available versions : i686-w64 & x86_64-w64

  


  



  with no success ; it creates a sample.mp4.bak file, even though the software says that the operation was successful

  



  


  can't insert any more links, because I got too little rep apparently

  


  



  

  4. Mp3tag (mp3tag.de/en)

  


  



  with no success ; I can successfully add the image as a cover, but it's not visible in the File Explorer. After saving it says Saved tag in 1 of 1 files. The picture can been seen in Mp3tag though as if it's applied.

  



  

  5. Tag&Rename (softpointer.com)

  


  



  with no success ; same story as with Mp3tag, I can apply and it's visible in the app, but not in File Explorer.

  



  

  6. mp4v2 (https:// code.google.com/archive/p/mp4v2/downloads)

  


  



  mp4tags.exe -picture sample.png sample.mp4

  



  with no success ; it executes with no (error)message

  



  I found it on this thread

  



  (https:// forum.videohelp.com/threads/388025-How-to-set-the-thumbnail-of-a-video-clip).

  



  Have used the updated version which is the Windows build

  



  (https:// forum.doom9.org/attachment.php ?attachmentid=14314&d=1407985798).

  



  

  7. iTunes

  


  



  iTunes 12.10.6.2 (Microsoft Store version)

  



  iTunes doesn't load the file into the library. I can run it fine though in QuickTime Player.

  



  I didn't notice the 'Home Videos' tab. Now I can see it in there. I tried to apply the image, and it applied it only inside iTunes... So it's still not working for me.

  



  I tried to convert the MP4 to M4A and then adding it to iTunes. I was finally successfully able to change the cover and it was visible in File Explorer. But that's not what I want.

  



  I know for a fact that it's possible, because I've seen pictures on the Internet and YT and different threads where an answer is upvoted.

  



  

  8. tag

  


  



  https:// github.com/b4winckler/tag

  



  The description is : Simple command line audio tag editor... After having to install millions of libraries and a package manager I was stuck with the compilation of the software, followed all the steps, didn't work.

  



  I've also tried using MP4art as suggested by a comment on another issue about this. He didn't include a link to it so I went looking and found another issue about this. One comment recommended MP4art as well, with a link that's dead.

  



  ---

  



  I believe I've used some other methods as well but can't think of them right now. Will update if I recall.

  



  Any help is greatly appreciated.

  


• Easy Tricks for Finding WebM Videos in YouTube

  9 août 2010, par noreply@blogger.com (John Luther)

  Since the WebM project launch, YouTube has been encoding videos uploaded at 720p or higher resolution in the WebM format. Today, the one million most popular videos of any size on YouTube are also available in the WebM format.

  We have instructions on our project site for finding these videos but they require adding a special parameter onto the end of each search query. All of the browsers that support WebM can create search shortcuts with custom parameters, however, so we’ve compiled instructions for making it very simple to search for WebM videos in YouTube.

  Important : First, make sure you have a supported browser and are enrolled in the YouTube HTML5 beta by going to http://youtube.com/html5 and clicking Enter the HTML5 Beta.

  Creating a WebM Search Shortcut

  Firefox 4 Beta :
  

  1. Select Bookmarks > Organize Bookmarks. A bookmark manager dialog opens.
  2. In the left column, choose a location for the new bookmark you’re creating. Next, choose Organize > New Bookmark (on MacOS click the gear icon). The new bookmark dialog opens.
  3. In the Name box, type WebM.
  4. In the Location box, type http://youtube.com/results?search_query=%s&webm=1.
  5. In the Keyword box, type webm.
  6. Click Add.

  Google Chrome Early Release Channel :
  

  1. On Windows and Linux, click the Chrome wrench icon in the toolbar and select Options. On MacOS, select Chrome > Preferences.
  2. On the Basics tab, click the Manage button in the Default Search section.
  3. On Windows and Linux, click Add. On MacOS X, click the plus (+) button.
  4. In the Name box, type WebM.
  5. In the Keyword box, type webm.
  6. In the URL box, type http://youtube.com/results?search_query=%s&webm=1.
  7. Click OK.

  Opera 10.60 and later :
  

  1. Go to http://youtube.com.
  2. Right-click in the YouTube search box at the top of the page and select Create Search. On MacOS, use Ctrl+click if you don’t a secondary mouse button enabled.
  3. In the Name box, type WebM.
  4. In the Keyword box, type webm.
  5. In the Address box, type http://youtube.com/results?search_query=%s&webm=1.
  6. Click OK.

  
  

  
  Now you’re ready to search. In the location box of the browser, type webm monster trucks. The YouTube search results page will open with a selection of monster truck videos encoded in the WebM format. When watching a video, look for the HTML5 WebM indicator in the player control bar.

  If you can’t find WebM videos it is most likely a browser cookie problem. Your enrollment in the YouTube HTML5 beta test is stored in a browser cookie (not in your YouTube or Google account), and that cookie can expire. Visit http://youtube.com/html5 and opt-in again to re-set the cookie.

  Directly Accessing WebM Videos by URL

  To find out if any YouTube video is available in WebM, simply add &html5=True (make sure True is capitalized) to the end of the video URL. If there is a WebM version of the video, it will open instead of the Flash version. For example :
  

  • Flash version : http://www.youtube.com/watch?v=Dz6gFokvOr0
  • WebM version : http://www.youtube.com/watch?v=Dz6gFokvOr0&html5=True