Tag Archives: capture

IP Video Source: Pure JPEG URLs and Software Version

Posted by on June 7, 2011 8 comments

This does not update the software with new features, but there are a few simple things worth mentioning explicitly.

The first is that virtual DirectShow camera device can be set up with both M-JPEG and JPEG URLs. That is, IP cameras which do not implement M-JPEG, or implement it in a buggy way (there is a *huge* deal of such out there) can still be set up to send video as individual video frames/images as long as they implement JPEG snapshots. This is taking place often at a lower frame rate, but still works.

The driver will automatically detect type of URL (by response from the device) and will choose best access method for the given URL.

Second is that if you are looking for IP Video Source software version, such as to check against available updates, it is here on the UI (right click the caption):

IP Video Source: 64-bit version, resolution flexibility, Adobe FMLE

Posted by on June 5, 2011 7 comments

The IP Video Source update provides several improvements to the driver:

  • copy/paste feature to backup, restore, or synchronize installed devices between 32-bit and 64-bit versions
  • 64-bit version and .MSI
  • dynamic video resizing (via Video Resizer DSP)
  • Adobe FMLE compatibility

Updates in greater detail follow.

Device Copy/Paste Feature

The video device management window is providing Copy and Paste buttons, which let user transfer device information, including name and settings, through clipboard for various purposes:

  • save data in order to be able to restore devices later
  • restore devices from saved list, or re-create from a list saved on another machine
  • duplicate a device
  • synchronize devices between 32-bit and 64-bit versions

The device data is a text, one line per device, lines in comma-separated values (CSV) format.

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DirectShow Video Source Filter for JPEG and M-JPEG IP Cameras

Posted by on May 23, 2011 1 comment

This implements a DirectShow driver/wrapper over a HTTP based JPEG/M-JPEG streamed video, widely available with IP cameras. Once installed, it provides a Start Menu shortcut to manage video capture devices, where a user can add/remove devices. The devices are automatically registered with DriectShow and are available to applications.

The compatibility list includes:

  • Windows SDK AmCap Sample (reference)
  • VideoLan VLC
  • Skype (see below)
  • Google Talk Video Chat
  • Luxriot (as rather an example as Luxriot has its own generic JPEG/M-JPEG device driver, however this still demonstrates compatibility and interoperability of applications)
  • GraphEdit, GraphStudio and similar tools

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How to dynamically change resolution for video preview

Posted by on September 30, 2009 No comments

From a conversation:

Q: I am using Web camera with DirectShow. Camera has only capture pin, so I am looking for the best way to switch resolution on the pin while graph is running. I would like to keep preview with smaller image size and when i would like to capture an image i would like to switch to full resolution. I have to use sample grabber callback since i need access to single image to process them. Is there a way to do that without stopping and starting a graph? This works but very slow between captures.

Is it possible to just reconnect the sample grabber only with new media changes and then resume the graph? Currently i just kill the graph and start it again, but it takes few seconds to do so, so I am looking the way to reduce that time.

There is no way to switch resolution on the running graph. There is a technique to dynamically start/stop individual filters and re-negotiate resolutions (media types), but it does not work for the majority of filters. Additionally to that Sample Grabber Filter cannot change resolution too, as it passes data through.

If you only have to use switched resolution for preview, you can use Geraint’s GMFBridge Toolkit to join two graphs, and a filter that changes resolution. Combining all that you will have a running capture graph that [also] renders video to a bridge sink. In the other graph you have another bridge sink that receives video from first graph and then you resize video to the resolution of interest already in the second graph. You can stop and reconfigure only second graph to update resolution and have first graph running and capturing. This is the best you can do, or just stop your single graph and change resolution this simple way.

So a solution, which is used by many, and I can recommend it too, is to use GMFBridge bridging. Additionally, you can find questions and answers on it on MSDN DirectShow Development Forum (search for “bridge” there). With a certain effort you can duplicate this with your own code but this is more or less ready to use solution and, again, the key advantage you have that you have two graphs which you can top independently.

Would it be possible to use smart tee as a splitter on the capture pin, and then use two sample grabbers on capture and preview, one with smaller resolution and the other one with higher one?

With a Smart Tee Filter you will still have 1 graph, so no individual resolution changes without stopping the graph. Additionally to that, Smart Tee Filter will deliver same frame on its output pins, so they will have to have one resolution and no resizing takes place inside.

Also, is it possible to run 2 graphs in the same time? Same device, 2 graphs, 2 sample grabbers.

Most likely no, for only one reason: you won’t be able to have two running filters for the same device, as source filter will exclusively lock the device. So capture filter will be a single filter. You can use Infinite Tee Pin Filter to split stream between 2+ processing lines. And you can use the same bridge to pass data into another graph for further processing.

MediaTools: Tone Source Filter to generate reference audio feed, dual Audio Source Filter and Virtual Audio Capture Device

Posted by on February 28, 2009 No comments

In order to obtain a reference audio source and especially useful for debugging purposes, including:

  • audio input device unrelated to physical device, to avoid conditions when device is already in use by someone else
  • non-zero audio signal which is independent of certain speaker or broadcasting service, including one that makes capture, transmission or rendering issues easily perceptible by human
  • configurable to provide different audio media types, including through well known DirectShow interfaces, such as IAMStreamConfig
  • configurable to present in system as both regular DirectShow Filter, and as an Audio Capture Source which can be enumerated by applications
  • to be able to check how exactly other applications are accessing and configuring audio capture source

I added a new filter to the Media Tools library, a Tone Source Filter. The filter generates PCM Audio data, either infinite sine waveform, or interrupted signal  of requested parameters:

Tone Source Filter General Property Page

The filter accepts connection on PCM media types with flexible sampling rates in range 8 KHz through 200 KHz, 8-bit audio and 1 channel. Media type is also configurable through or, if not configured this way, the first enumerated media type off the Output pin is also configurable through property page and/or persistent setting accessible via private IDispatch derived interface property.

Tone Source Filter Prefered Format Property Page

Additionally, the filter may configured as a system-wide available audio input device, such as for example available to VLC Media Player or Media Player Classic:

VLC Media Player's Option to use Tone Source Filter based device

In order to configure the filter as such device, the library exports function DoToneSourceFilterDevicePropertySheetModal, which can be called using rundll32 utility (“rundll32 Acquisition.dll,DoToneSourceFilterDevicePropertySheetModal” from command line):

Devices Property Page

A partial Visual C++ .NET 2008 source code is available from SVN, release binary included.

File and Class Summary

Acqusition.dll

Acqusition.dll (download) hosts the following classes:

  • DirectShow Filters
    • Tone Source Filter, to generate reference/debug audio data

Class Overview

Tone Source Filter

The filter generates uninterrupted or interrupted reference sine waveform in form of PCM audio data.

Remarks

The hosting library (DLL) exposes DoToneSourceFilterDevicePropertySheetModal function which provides GUI to configure the filter as one or more audio capture source device, which can be enumerated by System Device Enumerator.

JPEG Multi File Video Capture Source Filter, a virtual DirectShow camera

Posted by on January 17, 2009 11 comments

Provided that there already is a JPEG Multi File Source Filter that can act as a video source streaming video from local JPEG files, it looked to be useful to build a virtual camera on top of this filter. This is the main difference: an existing filter is generic and customizable: it requires to be provided a directory with the files, other settings may also apply. A virtual camera is the filter that has to work out of the box: a video enabled application, such as AMCap Sample, Media Player Classic, VideoLAN, Skype, Windows Media Encoder enumerates video capture sources, instantiate the one of the interest and it should already be ready to stream.

Implementation Details

The very first question is embedding of an existing filter into new filter. The two most common methods are:

  • COM aggregation
  • embedding a fully featured graph with a sink/renderer that intercepts media samples downstream and forwards to a higher level filter so that it streams them as a source filter

The COM aggregation methods is much easier in implementation but it is subject to a few constraints, the two most important of which are:

  • embedded filter should support instantiation as an aggregated object
  • it is the only underlying filter, not a chain of filters, which can produce required data

COM aggregation is quite fitting for the purpose, so the second embedding method is being left for another topic (with a certain luck to be appear very soon, a DirectShow video capture source filter for a real network/IP camera).

The next step is a check of sufficient implementation in an underlying filter. Obviously, a video source that pretends to be a live video capture source needs an endless stream of media samples, while original implementation streams JPEG files as media samples once only, we need an option to loop the streaming and automatically repeat the sequence.

Playback looping is added to the original JPEG Multi File Source Filter and its controlling private interface IJpegMultiFileSourceFilter received additional properties:

interface IJpegMultiFileSourceFilter : IDispatch
{
...
    [propget, id(2)] HRESULT AutoRepeat([out, retval] VARIANT_BOOL* pbAutoRepeat);
    [propput, id(2)] HRESULT AutoRepeat([in] VARIANT_BOOL bAutoRepeat);
    [propget, id(3)] HRESULT RepeatDelay([out, retval] LONG* pnRepeatDelay);
    [propput, id(3)] HRESULT RepeatDelay([in] LONG nRepeatDelay)

as well the new property page:

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