Q4OS Forum

Jerome

Member

Registered: 2016-02-26

Posts: 148

No video capture

I've recently created a screencast with vokoscreen but when playing back the video with VLC I just get a black screen. I also tried using Kazam but with the same result. Never had this problem before but have recently got a new monitor - could that be it? Any advice appreciated.

Dai_trying

Member

From: UK

Registered: 2015-12-14

Posts: 2,989

Re: No video capture

I'm not sure what the problem could be but I would take a look at the file to see if it is actually a good video file, one way to do this is to use the package mediainfo which will give you some good information like this :-

dai@q4asusi3:~/Videos/VideoIn$ mediainfo Prometheus.ts 
General
Complete name                            : Prometheus.ts
Format                                   : MPEG-PS
File size                                : 1.28 GiB
Duration                                 : 1 h 55 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 1 586 kb/s

Video
ID                                       : 224 (0xE0)
Format                                   : MPEG Video
Format version                           : Version 2
Format profile                           : Main@Main
Format settings, BVOP                    : Yes
Format settings, Matrix                  : Custom
Format settings, GOP                     : Variable
Duration                                 : 1 h 55 min
Bit rate mode                            : Variable
Bit rate                                 : 1 363 kb/s
Maximum bit rate                         : 15.0 Mb/s
Width                                    : 720 pixels
Height                                   : 576 pixels
Display aspect ratio                     : 16:9
Active Format Description                : Letterbox 16:9 image
Frame rate                               : 25.000 FPS
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.131
Stream size                              : 1.10 GiB (86%)

Audio
ID                                       : 192 (0xC0)
Format                                   : MPEG Audio
Format version                           : Version 1
Format profile                           : Layer 2
Duration                                 : 1 h 55 min
Bit rate mode                            : Constant
Bit rate                                 : 192 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 48.0 kHz
Compression mode                         : Lossy
Delay relative to video                  : 8 ms
Stream size                              : 159 MiB (12%)

You could post here the information and maybe it would shed some light. If the file appears to be good I would guess that you might be missing a codec, a possible solution to that would be to install the Q4OS codec package from the welcome screen (Install Proprietary Codecs)

Jerome

Member

Registered: 2016-02-26

Posts: 148

Re: No video capture

Hi Dai,

Thanks for the suggestions. I thought I'd already install the codecs but apparently I hadn't, however it made no difference. I ran mediainfo on a short mkv file I made with vokoscreen. Here is the output :

$ mediainfo vokoscreen-2019-02-26_17-24-24.mkv
General
Unique ID                                : 212521518564025764743681165322940677095 (0x9FE227D836BA797B31D0CC2B24ED7BE7)
Complete name                            : vokoscreen-2019-02-26_17-24-24.mkv
Format                                   : Matroska
Format version                           : Version 4 / Version 2
File size                                : 200 KiB
Duration                                 : 46 s 280 ms
Overall bit rate                         : 35.5 kb/s
Writing application                      : Lavf57.56.101
Writing library                          : Lavf57.56.101 / Lavf57.56.101
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L3.1
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 46 s 280 ms
Bit rate                                 : 34.8 kb/s
Width                                    : 700 pixels
Height                                   : 812 pixels
Display aspect ratio                     : 0.862
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.002
Stream size                              : 196 KiB (98%)
Writing library                          : x264 core 148 r2748 97eaef2
Encoding settings                        : cabac=1 / ref=1 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=2 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=6 / lookahead_threads=2 / 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=1 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=10 / rc=crf / mbtree=1 / crf=23.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Default                                  : Yes
Forced                                   : No
DURATION                                 : 00:00:46.280000000

I've no idea what any of this means or how to interpret it.

Jerome

Member

Registered: 2016-02-26

Posts: 148

Re: No video capture

I've just tried viewing the same mkv file on my netbook which is also running Scorpion, and it was ok, which seems to suggest that the problem is hardware specific.

Dai_trying

Member

From: UK

Registered: 2015-12-14

Posts: 2,989

Re: No video capture

That is a possibility, I would try another Video player, maybe mpv? to see if that works as I have found it to be really reliable, I think it would be quite unusual for it to be a hardware problem unless you have no video drivers (and/or firmware if required) installed. Could you post output of inxi -G?

Jerome

Member

Registered: 2016-02-26

Posts: 148

Re: No video capture

Here you go :

~$ inxi -G
Graphics:  Card: Advanced Micro Devices [AMD/ATI] Mullins [Radeon R3 Graphics]
           Display Server: X.Org 1.19.2 drivers: ati,radeon (unloaded: modesetting,fbdev,vesa)
           Resolution: 1280x1024@60.02hz
           GLX Renderer: Gallium 0.4 on AMD MULLINS (DRM 2.49.0 / 4.9.0-8-amd64, LLVM 3.9.1)
           GLX Version: 3.0 Mesa 13.0.6

I'll try mpv on the file.

Jerome

Member

Registered: 2016-02-26

Posts: 148

Re: No video capture

Ok, the plot thickens... mpv didn't work; when I ran it with the file as the argument a window opened up which looked like a screenshot of the portion of the screen covered by the window. So then I installed mplayer, and it worked!

Strange, why should VLC run the file ok on my netbook but not my desktop? unless there's an issue with the 64 bit version (my netbook is 32 bit). So right now not sure where the problem lies, but at least I know which media player will actually play back the video file correctly.

This is the output from mplayer :

Playing vokoscreen-2019-02-26_17-24-24.mkv.
libavformat version 57.56.101 (external)
Mismatching header version 57.56.100
libavformat file format detected.
[lavf] stream 0: video (h264), -vid 0
VIDEO:  [H264]  700x812  0bpp  25.000 fps    0.0 kbps ( 0.0 kbyte/s)
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
libavcodec version 57.64.101 (external)
Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
==========================================================================
Clip info:
ENCODER: Lavf57.56.101
Load subtitles in ./
Audio: no sound
Starting playback...
Movie-Aspect is undefined - no prescaling applied.
VO: [vdpau] 700x812 => 700x812 Planar YV12
V:  46.2   0/  0 11%  2%  0.0% 0 0

Exiting... (End of file)

Last edited by Jerome (2019-02-26 19:50)

Dai_trying

Member

From: UK

Registered: 2015-12-14

Posts: 2,989

Re: No video capture

You could check on the notebook which plugins are installed for VLC and compare it to what is installed on your other machine, a simple way to do this would be to run

dpkg --get-selections | grep -i vlc

on both machines and compare them to find any differences.

Jerome

Member

Registered: 2016-02-26

Posts: 148

Re: No video capture

There are no differences between the versions, at least not in terms of plugins. I installed Trinity's kmplayer and it also worked fine (although it's only a frontend for mplayer and xine, so not surprising it worked since mplayer did). VLC now seems redundant so I uninstalled it. ;-)

Dai_trying

Member

From: UK

Registered: 2015-12-14

Posts: 2,989

Re: No video capture

I had a lot of issues with VLC during the last six months or so which is why I install and mainly use mpv now although I also have smplayer installed and occaisionally use that as well.

Jerome

Member

Registered: 2016-02-26

Posts: 148

Re: No video capture

I had to remove kmplayer because there was a nasty bug. After playing the file the screen went black and you found yourself logged out of the current session! Is it really too much to ask to get a decent multimedia player on Linux? Anyway I installed smplayer and it seems good (so far).

Last edited by Jerome (2019-02-26 22:11)