|Version 11 (modified by rogerdpack, 4 years ago) (diff)|
FFmpeg can take input from "directshow" devices on your windows computer. These are typically video or audio devices that are attached.
c:\> ffmpeg -list_devices true -f dshow -i dummy ffmpeg version N-45279-g6b86dd5... --enable-runtime-cpudetect libavutil 51. 74.100 / 51. 74.100 libavcodec 54. 65.100 / 54. 65.100 libavformat 54. 31.100 / 54. 31.100 libavdevice 54. 3.100 / 54. 3.100 libavfilter 3. 19.102 / 3. 19.102 libswscale 2. 1.101 / 2. 1.101 libswresample 0. 16.100 / 0. 16.100 [dshow @ 03ACF580] DirectShow video devices [dshow @ 03ACF580] "Integrated Camera" [dshow @ 03ACF580] "screen-capture-recorder" [dshow @ 03ACF580] DirectShow audio devices [dshow @ 03ACF580] "Internal Microphone (Conexant 2" [dshow @ 03ACF580] "virtual-audio-capturer" dummy: Immediate exit requested
Then use the listed devices like
c:\> ffmpeg -f dshow -i video="Integrated Camera" out.mp4
You can also pass the device certain parameters that it needs, for instance a webcam might allow you to capture it in "1024x768" at up to max 5 fps, or allow you to capture at "640x480" at 30 fps. You can enumerate the options like this:
c:\> ffmpeg -f dshow -list_options true -i video=<video device> ex:
ffmpeg -f dshow -list_options true -i video="Integrated Camera" ffmpeg version N-45279-g6b86dd5 Copyright (c) 2000-2012 the FFmpeg developers built on Oct 10 2012 17:30:47 with gcc 4.7.1 (GCC) configuration:... libavutil 51. 74.100 / 51. 74.100 libavcodec 54. 65.100 / 54. 65.100 libavformat 54. 31.100 / 54. 31.100 libavdevice 54. 3.100 / 54. 3.100 libavfilter 3. 19.102 / 3. 19.102 libswscale 2. 1.101 / 2. 1.101 libswresample 0. 16.100 / 0. 16.100 [dshow @ 01D4F3E0] DirectShow video device options [dshow @ 01D4F3E0] Pin "Capture" [dshow @ 01D4F3E0] pixel_format=yuyv422 min s=640x480 fps=15 max s=640x480 fps=30 [dshow @ 01D4F3E0] pixel_format=yuyv422 min s=1280x720 fps=7.5 max s=1280x720 fps=7.5 [dshow @ 01D4F3E0] vcodec=mjpeg min s=640x480 fps=15 max s=640x480 fps=30 [dshow @ 01D4F3E0] vcodec=mjpeg min s=1280x720 fps=15 max s=1280x720 fps=30 video=Integrated Camera: Immediate exit requested
You can see in this particular instance that it can either stream it to you in a "raw pixel_format" (yuyv422 in this case), or as an mjpeg stream.
You can specify the type (mjpeg) and size (1280x720) and frame rate to tell the device to give you (15 fps), like this:
ffmpeg -f dshow -s 1280x720 -r 15 -vcodec mjpeg -i video="Integrated Camera" out.avi
Sometimes it helps to specify "-vcodec copy" to save on cpu to re-encode, if you can receive the data in some type of pre-encoded format, like mjpeg in this instance.
Also this note that "The input string is in the format video=<video device name>:audio=<audio device name>. It is possible to have two separate inputs (like -f dshow -i audio=foo -f dshow -i video=bar) but my limited tests had shown a better synchronism when both were used in the same input."
See here for a list of more dshow options you can specify, for instance you can decrease latency on audio devices, specify a video by "index" if 2 have the same name displayed, etc.
By default FFmpeg captures frames from the input, and then (does whatever you told it to do, for instance, re-encoding them and saving them to an output file). By default if it receives a frame "too early" (while the previous frame isn't finished yet), it will discard that frame, so that it can keep up the the real time input. You can adjust this by setting the "-rtbufsize" parameter, though note that if your encoding process can't keep up, eventually you'll still start losing frames just the same (and using it at all can introduce a bit of latency). It may be helpful to still specify some buffer, however, otherwise frames may be needlessly dropped.
See StreamingGuide for some tips on tweaking encoding (sections latency and cpu usage). For instance, you could save it to a very fast codec, then re-encode it later.
If you have a video capture card (ex: AverMedia, possibly some BlackMagic, though it may be a separate unrelated problem, and also some BlackMagic cards don't have the right inputs set up ask on the forum), it may not work (yet) out of the box with FFmpeg, as it lacks crossbar support presently. The work around currently is to install the AmerecTV software, which presents the capture card as directshow devices, then input the AmerecTV directshow devices into your FFmpeg. See here.
Using DirectShow with libav*
Basically, you can accept input dshow input into you program that uses, see Using libav* to know what libav does. See http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=15&t=274&p=902&hilit=dictionary#p902
How to programmatically enumerate devices
FFmpeg doesnt' provide a native way to do this yet, but you can lookup the devices yourself, or just parse ffmepg's standard out:
FFmpeg can also take DirectShow input by creating an avisynth file (.avs file) that itself gets input from a graphedit file, which graphedit file exposes a pin of your capture source or any filter really, ex ("yo.avs") with this content:
!DirectShowSource("push2.GRF", fps=35, audio=False, framecount=1000000)
ffdshow tryouts is a separate project that basically wraps FFmpeg's core source (libavcodec, etc.) and then presents them as filter wrappers that your normal Windows applications can use for decoding video, etc. It's not related to "ffmpeg.exe" directly, at all.
You can ask questions/comments about DirectShow on the zeranoe forum.