Hi,
I have a web cam that supports hardware MJPEG stream:
user@router:~> v4l2-ctl --list-formats
ioctl: VIDIOC_ENUM_FMT
Index : 0
Type : Video Capture
Pixel Format: 'MJPG' (compressed)
Name : MJPEG
Index : 1
Type : Video Capture
Pixel Format: 'YUYV'
Name : YUV 4:2:2 (YUYV)
user@router:~> v4l2-ctl -d /dev/video0 -v width=960,height=720,pixelformat=MJPEG
user@router:~> v4l2-ctl --all
Driver Info (not using libv4l2):
Driver name : uvcvideo
Card type : UVC Camera (046d:0991)
Bus info : usb-0000:00:1d.7-4
Driver version: 3.4.6
Capabilities : 0x04000001
Video Capture
Streaming
Format Video Capture:
Width/Height : 960/720
Pixel Format : 'MJPG'
Field : None
Bytes per Line: 0
Size Image : 409600
Colorspace : SRGB
Crop Capability Video Capture:
Bounds : Left 0, Top 0, Width 960, Height 720
Default : Left 0, Top 0, Width 960, Height 720
Pixel Aspect: 1/1
Video input : 0 (Camera 1: ok)
Streaming Parameters Video Capture:
Capabilities : timeperframe
Frames per second: 10.000 (10/1)
Read buffers : 0
I want to capture raw mjpeg stream without re-encode or transcode.
VLC does that:
user@router:~> vlc -I dummy v4l2:///dev/video0:width=960:height=720:fps=15 :v4l2-chroma=MJPG :v4l2-fps=15 --sout=file/asf:mjpeg-vlc.asf
VLC media player 2.0.3 Twoflower (revision 2.0.2-93-g77aa89e)
[0x88c51d8] main interface error: no suitable interface module
[0x882d3f0] main libvlc error: interface "globalhotkeys,none" initialization failed
[0x88c51d8] dummy interface: using the dummy interface module...
^C
user@router:~mediainfo mjpeg-vlc.asf
General
Complete name : mjpeg-vlc.asf
Format : Windows Media
File size : 5.28 MiB
Duration : 8s 532ms
Overall bit rate : 5 189 Kbps
Maximum Overall bit rate : 1 bps
Video
ID : 1
Format : JPEG
Codec ID : MJPG
Description of the codec : Unknown Video
Bit rate : 4 977 Kbps
Width : 960 pixels
Height : 720 pixels
Display aspect ratio : 4:3
Color space : YUV
Bit depth : 8 bits
Compression mode : Lossy
ffmpeg does that:
user@router:~> ffmpeg -f video4linux2 -vcodec mjpeg -r 15 -i /dev/video0 -vcodec copy mjpeg-ffmpeg.avi
ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
built on Jun 10 2012 22:43:48 with gcc 4.7.1 20120723 [gcc-4_7-branch revision 189773]
configuration: --shlibdir=/usr/lib --prefix=/usr --mandir=/usr/share/man --libdir=/usr/lib --enable-shared --disable-static --enable-debug --disable-stripping --extra-cflags='-fomit-frame-pointer -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gsm' --enable-gpl --enable-x11grab --enable-version3 --enable-pthreads --enable-avfilter --enable-libpulse --enable-libvpx --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libxvid --enable-libx264 --enable-libschroedinger --enable-libgsm --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-postproc --enable-libdc1394 --enable-librtmp --enable-libfreetype --enable-avresample
WARNING: library configuration mismatch
avutil configuration: --enable-shared --disable-static --disable-doc --prefix=/usr --libdir=/usr/lib --shlibdir=/usr/lib --disable-stripping --extra-cflags='-fomit-frame-pointer -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g'
libavutil 51. 54.100 / 51. 54.100
libavcodec 54. 23.100 / 54. 23.100
libavformat 54. 6.100 / 54. 6.100
libavdevice 54. 0.100 / 54. 0.100
libavfilter 2. 77.100 / 2. 77.100
libswscale 2. 1.100 / 2. 1.100
libswresample 0. 15.100 / 0. 15.100
libpostproc 52. 0.100 / 52. 0.100
[video4linux2,v4l2 @ 0x8f7d540] Estimating duration from bitrate, this may be inaccurate
Input #0, video4linux2,v4l2, from '/dev/video0':
Duration: N/A, start: 11156.932290, bitrate: N/A
Stream #0:0: Video: mjpeg, yuvj422p, 960x720, -2 kb/s, 15 tbr, 1000k tbn, 15 tbc
Output #0, avi, to 'mjpeg-ffmpeg.avi':
Metadata:
ISFT : Lavf54.6.100
Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj422p, 960x720, q=2-31, -2 kb/s, 30 tbn, 30 tbc
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, ?] for help
frame= 96 fps=9.1 q=-1.0 Lsize= 8045kB time=00:00:10.56 bitrate=6237.0kbits/s
video:8032kB audio:0kB global headers:0kB muxing overhead 0.162122%
Received signal 2: terminating.
user@router:~> mediainfo mjpeg-ffmpeg.avi
General
Complete name : mjpeg-ffmpeg.avi
Format : AVI
Format/Info : Audio Video Interleave
File size : 7.86 MiB
Duration : 10s 567ms
Overall bit rate : 6 237 Kbps
Writing application : Lavf54.6.100
Video
ID : 0
Format : JPEG
Codec ID : MJPG
Duration : 10s 567ms
Bit rate : 6 227 Kbps
Width : 960 pixels
Height : 720 pixels
Display aspect ratio : 4:3
Frame rate : 30.000 fps
Color space : YUV
Chroma subsampling : 4:2:2
Bit depth : 8 bits
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.300
Stream size : 7.84 MiB (100%)
But mencoder always captures YUV instead of mjpeg:
user@router:~> mencoder tv:// -tv driver=v4l2:width=960:height=720:fps=15:mjpeg -nosound -ovc copy -o mjpeg-mencoder.avi
MEncoder dev-SVN-r35127-4.7-openSUSE Linux 12.2 (i586)-Packman (C) 2000-2012 MPlayer Team
success: format: 9 data: 0x0 - 0x0
TV file format detected.
Selected driver: v4l2
name: Video 4 Linux 2 input
author: Martin Olschewski <olschewski@zpr.uni-koeln.de>
comment: first try, more to come ;-)
v4l2: your device driver does not support VIDIOC_G_STD ioctl, VIDIOC_G_PARM was used instead.
Selected device: UVC Camera (046d:0991)
Capabilities: video capture streaming
supported norms:
inputs: 0 = Camera 1;
Current input: 0
Current format: MJPEG
v4l2: ioctl set format failed: Invalid argument
v4l2: ioctl set format failed: Invalid argument
v4l2: ioctl set format failed: Invalid argument
tv.c: norm_from_string(pal): Bogus norm parameter, setting default.
v4l2: ioctl enum norm failed: Invalid argument
Error: Cannot set norm!
Selected input hasn't got a tuner!
v4l2: ioctl set mute failed: Invalid argument
v4l2: ioctl query control failed: Invalid argument
[V] filefmt:9 fourcc:0x32595559 size:960x720 fps:15.000 ftime:=0.0667
videocodec: framecopy (960x720 24bpp fourcc=32595559)
Forcing audio preload to 0, max pts correction to 0.
v4l2: select timeout
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not writing vprp header.
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not writing vprp header.
Pos: 0.0s 1f ( 0%) 0.65fps Trem: 0min 0mb A-V:0.000 [0:0]
v4l2: select timeout
Skipping frame!
Pos: 0.1s 2f ( 0%) 0.84fps Trem: 0min 0mb A-V:0.000 [0:0]
Skipping frame!
Pos: 0.1s 3f ( 0%) 0.98fps Trem: 0min 0mb A-V:0.000 [0:0]
v4l2: select timeout
Skipping frame!
Pos: 0.1s 4f ( 0%) 1.01fps Trem: 0min 0mb A-V:0.000 [0:0]
v4l2: select timeout
Skipping frame!
Pos: 0.1s 5f ( 0%) 1.04fps Trem: 0min 0mb A-V:0.000 [0:0]
Skipping frame!
Pos: 0.2s 9f ( 0%) 1.63fps Trem: 0min 0mb A-V:0.000 [0:0]
1 duplicate frame(s)!
Pos: 0.3s 10f ( 0%) 1.77fps Trem: 0min 0mb A-V:0.000 [0:0]
1 duplicate frame(s)!
Pos: 0.5s 12f ( 0%) 2.04fps Trem: 0min 0mb A-V:0.000 [0:0]
1 duplicate frame(s)!
Pos: 0.7s 14f ( 0%) 2.29fps Trem: 0min 0mb A-V:0.000 [0:0]
1 duplicate frame(s)!
Pos: 0.9s 16f ( 0%) 2.47fps Trem: 0min 0mb A-V:0.000 [0:0]
1 duplicate frame(s)!
Pos: 1.1s 18f ( 0%) 2.77fps Trem: 0min 0mb A-V:0.000 [126855:0]
1 duplicate frame(s)!
Pos: 1.3s 20f ( 0%) 2.99fps Trem: 0min 0mb A-V:0.000 [124416:0]
1 duplicate frame(s)!
Pos: 1.4s 21f ( 0%) 3.05fps Trem: 0min 0mb A-V:0.000 [126390:0]
1 duplicate frame(s)!
Pos: 1.5s 22f ( 0%) 3.20fps Trem: 0min 0mb A-V:0.000 [122612:0]
1 duplicate frame(s)!
^C
s: 1.7s 23f ( 0%) 3.25fps Trem: 0min 0mb A-V:0.000 [119439:0]
1 duplicate frame(s)!
Pos: 1.8s 24f ( 0%) 3.31fps Trem: 0min 0mb A-V:0.000 [116735:0]
Writing index...
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not writing vprp header.
Video stream: 108685.242 kbit/s (13585655 B/s) size: 26265600 bytes 1.933 secs 24 frames
v4l2: ioctl set mute failed: Invalid argument
v4l2: 21 frames successfully processed, 13 frames dropped.
user@router:~> mediainfo mjpeg-mencoder.avi
General
Complete name : mjpeg-mencoder.avi
Format : AVI
Format/Info : Audio Video Interleave
File size : 25.1 MiB
Duration : 1s 933ms
Overall bit rate : 109 Mbps
Writing application : MEncoder dev-SVN-r35127-4.7-openSUSE Linux 12.2 (i586)-Packman
Writing library : MPlayer
Video
ID : 0
Format : YUV
Codec ID : YUY2
Codec ID/Info : YUV 4:2:2 as for UYVY but with different component ordering within the u_int32 macropixel
Duration : 1s 933ms
Bit rate : 109 Mbps
Width : 960 pixels
Height : 720 pixels
Display aspect ratio : 4:3
Frame rate : 15.000 fps
Color space : YUV
Chroma subsampling : 4:2:2
Compression mode : Lossless
Bits/(Pixel*Frame) : 10.483
Stream size : 25.0 MiB (100%)
How to force mencoder to read MJPEG stream?
