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Differing amounts of transmission delay might affect any two packets in a multicast stream. Jitter compares the transmission delays for two packets and measures the scope of difference between them.
Each DMP reserves 5 MB in its RAM to buffer incoming packets from multicast streams. This method is meant to reduce the risk of jitter during playback. The jitter buffer capacity of DMPs is sufficient to store from an MPEG-2 transport stream:
Some of the metadata inside MPEG-2 files and streams is meant to ensure that:
The metadata element that controls these behaviors is called the presentation time stamp, or PTS. The original encoding of an MPEG-2 file automatically adds PTS metadata values to it. These values state when a video or audio frame must be presented to the client system, relative to the timing of nearby frames. So, in a typical MPEG-2 transport stream:
When your DMP receives an MPEG-2 transport stream, it inspects the packets to find and make use of PTS values within them. The first time that your DMP finds a PTS value in a transport stream, it generates a system time clock (STC) value for its own use. Then, multiple events occur in tandem.
If anything delays a PTS value from arriving when the corresponding STC value anticipates that it should arrive, the visible result is latency during playback. This occurs because the jitter buffer must hold more data than it is intended to hold.
Many factors might affect how “late” a PTS value can be, including network congestion, CPU load on the DMP, and how the originating encoder is configured. For example, how does the encoder interleave audio with video, and does it use B frames?
The arrival time for any PTS value can never be guaranteed, even in the best networks.
You can reduce the risk of latency and limit its effects. Simply configure the originating encoder to:
Complete this sequence of procedures to upload supported assets to the SD card in your DMP, and then play them.
1. Enable FTP and SFTP access.
See Enable or Disable Types of Access to Your DMP.
2. Configure login credentials for the FTP and SFTP user accounts.
See Manage and Edit Passwords.
3. Upload assets to the /tmp/ftproot/usb_1 subdirectory on your DMP.
4. Play the media that you uploaded.
See Watch or Stop Video from a File Stored on Your DMP.
Note DMPs do not support multicast streaming over Wi-Fi.
You can control how your DMP synchronizes audio with video in a multicast stream.
Step 1 Depending on your DMP model and its firmware version, do one of the following.
Step 2 Enter or edit required values in the Multicast Jitter Buffer Control area, and then click Apply.
Step 3 Stop. You have completed this procedure.
Step 1 Click to fill the screen on your DMP display with only the video content plane.
The HTML content plane is hidden.
Step 2 Stop. You have completed this procedure.
You can save supported media files to a USB flash drive, attach that drive to your DMP, and then show the files on the attached DMP display.
Step 1 Move copies of the relevant media files from their source device to the root level of the USB flash drive that you will use.
Step 2 Unmount the USB flash drive from the source device, and then attach it to your DMP.
Step 4 Stop. You have completed this procedure
You can start or stop playback of video from a UDP multicast stream.
Step 1 Click Video Multicast in the Display Actions list.
Note DMPs do not support multicast streaming over Wi-Fi.
Step 2 Enter or edit the required values.
Step 3 Do one of the following.
Step 4 Stop. You have completed this procedure.
To show on your DMP display the video content from an HTTP URL, or to stop showing that video content, do the following.
Step 1 Click Video URL in the Display Actions list.
Step 2 Enter or edit the required values.
Step 3 Do one of the following.
There might be a delay of as long as 3 seconds.
Step 4 Stop. You have completed this procedure.
You can start or stop playback of video from DMP local storage. The storage volume might be the internal SD card or an external USB flash drive or USB hard drive that is mounted.
Step 1 Click Play Video File Stored Locally in the Display Actions list.
Step 2 Enter or edit the required values.
Step 3 Do one of the following.
Step 4 Stop. You have completed this procedure.
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Video Multicast |
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Play Video File Stored Locally |
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