From 15cc1733e0e7bf005362fad61a3ccbbefe1cbceb Mon Sep 17 00:00:00 2001 From: Klaus Schmidinger Date: Sun, 4 Aug 2002 14:57:29 +0200 Subject: Changed the cDevice class to allow plugins to implement their own devices --- PLUGINS.html | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) (limited to 'PLUGINS.html') diff --git a/PLUGINS.html b/PLUGINS.html index 2a66e88d..c9d6c542 100644 --- a/PLUGINS.html +++ b/PLUGINS.html @@ -1152,5 +1152,122 @@ of these functions, and VDR/osd.c to see how VDR opens the OSD and sets up its windows and color depths). +
  +

Devices

+ +
Expanding the possibilities

+ +By default VDR is based on using DVB PCI cards that are supported by the +LinuxDVB driver. However, a plugin can implement additional devices that +can be used as sources of MPEG data for viewing or recording, and also +as output devices for replaying. Such a device can be a physical card +that is installed in the PC (like, for instance, an MPEG encoder card that +allows the analog signal of a proprietary set-top box to be integrated +into a VDR system; or an analog TV receiver card, which does the MPEG encoding +"on the fly" - assuming your machine is fast enough), or just a software program that takes an MPEG data +stream and displays it, for instance, on an existing graphics adapter. +

+To implement an additional device, a plugin must derive a class from cDevice: + +



+#include <vdr/device.h>
+
+class cMyDevice : public cDevice {
+  ...
+  };
+

+ +The derived class must implement several virtual functions, according to +the abilities this new class of devices can provide. See the comments in the +file VDR/device.h for more information on the various functions, +and also VDR/dvbdevice.[hc] for details on the implementation of +the cDvbDevice, which is used to access the DVB PCI cards. +

+Channel selection +

+If the new device can receive, it most likely needs to provide a way of +selecting which channel it shall tune to: + +



+virtual bool SetChannelDevice(const cChannel *Channel);
+

+ +This function will be called with the desired channel and shall return whether +tuning to it was successful. +

+Recording +

+A device that can be used for recording must implement the functions + +



+virtual bool SetPid(cPidHandle *Handle, int Type, bool On);
+virtual bool OpenDvr(void);
+virtual void CloseDvr(void);
+virtual int GetTSPacket(uchar *Data);
+

+ +which allow VDR to set the PIDs that shall be recorded, set up the device fro +recording (and shut it down again), and receive the MPEG data stream. The data +must be delivered in the form of a Transport Stream (TS), which consists of +packets that are all 188 bytes in size. Each call to GetTSPacket() +must deliver exactly one such packet (if one is currently available). +

+If this device allows receiving several different data streams, it can +implement + +



+virtual bool CanBeReUsed(int Frequency, int Vpid);
+

+ +to indicate this to VDR. +

+Replaying +

+The functions to implement replaying capabilites are + +



+virtual bool HasDecoder(void) const;
+virtual int SetPlayMode(bool On);
+virtual void TrickSpeed(int Speed);
+virtual void Clear(void);
+virtual void Play(void);
+virtual void Freeze(void);
+virtual void Mute(void);
+virtual void StillPicture(const uchar *Data, int Length);
+virtual int PlayVideo(const uchar *Data, int Length);
+

+ +In addition, the following functions may be implemented to provide further +functionality: + +



+virtual bool GrabImage(const char *FileName, bool Jpeg = true, int Quality = -1, int Si
+virtual void SetVideoFormat(bool VideoFormat16_9);
+virtual void SetVolumeDevice(int Volume);
+

+ +Initializing new devices +

+A derived cDevice class shall implement a static function + +



+static bool Initialize(void);
+

+ +in which it determines whether the necessary hardware to run this sort of +device is actually present in this machine (or whatever other prerequisites +might be important), and then creates as many device objects as necessary. +See VDR/dvbdevice.c for the implementation of the cDvbDevice +initialize function. +

+A plugin that adds devices to a VDR instance shall call this initializing +function from its Start() function. +

+Nothing needs to be done to shut down the devices. VDR will automatically +shut down (delete) all devices when the program terminates. It is therefore +important that the devices are created on the heap, using the new +operator! +

+ -- cgit v1.2.3