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General

Timeshifting

Minimum

Minimum files is the number of files that is used for timeshifting when you are watching live tv. This allows you to jump back in the tv stream in case you missed something. After the maximum timeshift size is reached (Minimum x Filesize), the oldest content will be overwritten with the new one.

Maximum

Maximum files is used when you pause the tv. In this case the tv signal is still saved into the timeshift buffer so that when you resume playback you can watch everything up until the point of the live tv. If you switch the channel while you are not watching tv at live point, the new channel will be tuned and you will start watching at the livepoint of the new channel. You can still go back and watch the timeshift buffer of the old channel up until the point where you switched channels, except when the switch requires using different card. Be aware that once the maximum amount of timeshifting has been reached (Maximum x Filesize) MediaPortal will stop writing the tv stream to the timeshift buffer. So if you pause for a long time, then start watching again you can only watch until the point where the timeshift buffer was full, at which point you will be set to the livepoint when this happened. This means that you will lose any data from the point where the buffer was full until the point where you resumed watching.

Filesize

The filesize of each individual timeshift buffer file. Depending on the type of content a given time of tv stream can be stored into the file (see Timeshifting info below).

Wait for unscrambled signal

When a channel is scrambled (decrypted) the tv server will try to decrypt the tv stream as long as the tv card has a cam (see CAM enabled and present for this card). If the tv server wasn't able to tune into the channel after this time(default: 5 seconds) it will time out.

Wait for timeshifting file

When the tv server starts timeshifting, the timeshifting files are created. The clients access these files (either directly if they are on the same machine or through the streaming service) to show the tv stream. If the client wasn't able to read from the timeshifting file within this period of time (default: 15 seconds) it will give up and show an error message.

Note that these settings apply per tuner. If you have limited disk space (such as if Timeshifting to a Ramdisk) you may need to modify these settings to ensure there is enough space for all tuners sharing a drive for timeshifting. This will reduce the length of the buffer available for pause or rewind of LiveTV.

The logic of timeshifting

A few things have already been explained in the section above, this will give an even more detailed explanation of what happens when you watch tv with MediaPortal. The logic of timeshifting is quite complicated. You only have to read this if you have problems related to timeshifting or are really interested in the details of how timeshifting works in MediaPortal.

When you watch tv the tv server tunes into a channel and starts receiving the tv signal. This signal is then written to a temporary file, called timeshift buffer (*.ts) by a component called tswriter. If a client wants to watch the tv signal it reads from this timeshift buffer with a component called tsreader. If the client is on the same computer as the server the file is accessed directly. If the client is on another computer the streaming component streamingserver reads the local timeshift buffer and then sends the video over the network using the rtsp protocol.

If the channel is scrambled, the tswriter sends the PIDs to the CAM for decryption. The time this is allowed to take is controlled with the setting Wait for unscrambled signal. If the tv server was able to decrypt the tv stream, the tswriter starts writing the tv stream into the timeshift files. At the same time the client's tsreader tries to start reading these file so it can output the tv signal to the screen. If the tsreader fails for longer than Wait for timeshifting file seconds to read from this file it will result in an error.

If all goes well and the client starts outputting the tv signal, the tsreader always stays at the end of the timeshift buffer (this position is called live point). At the same time the tswriter continues to write the tv stream into the timeshift buffer, which actually consists of one or more files (called tsbuffer files). Each file is Filesize MBytes large and can contain a certain time of tv signal depending on the content of the tv stream (SD/HD, subtitles, sound, etc.). After the file has reached the maximum size a new file is created and the tv stream is saved into this file. This is repeated until the Minimum amount of files have been created at which point the oldest file is being reused. This means that you can only go as far back in the tv stream as there is place in Minimum x Filesize MByte of storage. You can see an estimation of these values in the Timeshifting Info area of this section.

Now if you pause the live tv (maybe take a break, go for a walk or feed the dog) the tsreader stays at the current position while the tswriter still writes the tv stream to the timeshift buffer. This allows you to later on resume tv from the previous point and either watch time-displaced at normal speed or speed forward/jump forward to the live point. During the paused state the tswriter will continue to create new tsbuffer files until the Maximum number of files has been reached, at which point the tswriter will stop to write the tv stream to the hard disk. This means that all tv signal between this time (Maximum number of tsbuffer files has been reached) and the time when you resume watching tv, the tv stream is lost. When you later actually reach this point you will be forwarded to the time at which the tswriter started writing to the tsbuffer again (Livepoint when you resumed watching).

Timeshifting Info

Here you can see an approximation of how much drive space will be used by the timeshift buffern and how much hd or sd content fit's into the timeshift buffer.

 

Folders

In this screen you can change the folders in which the timeshifting files are saved. You can choose a seperate folder for each of your card or one folder for all cards (Press "Same timeshift folder for all cards").

 

Timeshifting to a RAM Drive

Some people prefer to setup mediaportal to timeshift to a ram drive rather than a physical hard drive. The advantages are less noise and physical wear on the hard drive.  Some users report increased responsiveness with pausing and fast forward/rewinging tv with a ram drive, although any performance gain is likely to be quite small. Please view the mediaportal wiki page on ramdisks and timeshifting for more info
2013-01-20T06:10:05Z

   

 

2 Comments

  1. says:
    I'm adding a link to ramdrive for timeshifting wiki page. If someone thinks this is inappropriate just go ahead and delete it
    Posted Jan, 20 2013 06:05

  2. says:
    Replaced picture from "General" tab with current one from 1.2.1
    Posted Okt, 17 2011 15:23