User Guide for Cisco Digital Media Player Device Manager 5.2.x
Video and Audio
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Configure Video and Audio Settings

Table Of Contents

Configure Video and Audio Settings

Concepts

Performance Factors

Understand Jitter

Understand the Jitter Buffer

Understand Presentation Time Stamp (PTS) Values

Understand System Time Clock (STC) Values

Understand Why PTS-STC Discrepencies Flood the Buffer and Cause Latency

Guidelines

Limit and Reduce Latency

Workflows

Workflow to Play Assets from the Memory Card

Procedures

Configure Settings

Adjust Jitter Buffer Control (Advanced Multicast) Settings

Turn Full-Screen Video Mode On or Off

Play Media

Play Assets from a USB Flash Drive

Watch or Stop Video from a UDP Multicast Stream

Watch or Stop Video from an HTTP URL

Watch or Stop Video from a File Stored on Your DMP

Reference

UI Reference Topics

UI Reference: Elements to Define Video Multicast Settings

UI Reference: Elements to Define Video URLs

UI Reference: Elements to Play Locally Stored Video

UI Reference: Elements to Define Jitter Buffer (Advanced Multicast) Settings


Configure Video and Audio Settings


Revised: November 24, 2010

Concepts

Procedures

Reference

Concepts

Performance Factors

Guidelines

Workflows

Performance Factors

Understand Jitter

Understand the Jitter Buffer

Understand Presentation Time Stamp (PTS) Values

Understand System Time Clock (STC) Values

Understand Why PTS-STC Discrepencies Flood the Buffer and Cause Latency

Understand Jitter

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.

Understand the Jitter Buffer

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:

8 seconds of SD video, encoded to 5 Mbps

2.2 seconds of HD video, encoded to 18 Mbps

Understand Presentation Time Stamp (PTS) Values

Some of the metadata inside MPEG-2 files and streams is meant to ensure that:

Video and audio data are synchronized correctly during playback.

Playback occurs at the correct speed.

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:

Each video frame travels with one PTS value that describes it uniquely.

Several audio frames travel together with one PTS value that describes them collectively.

Understand System Time Clock (STC) Values

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.

Approximately 24 milliseconds after your DMP recognizes that the multicast stream has delivered a PTS value, its generated STC value triggers playback of the corresponding video and audio data. This brief delay contributes to proper playback of the stream.

Your DMP considers the video frame rate and other factors to make programatic assumptions about what the second PTS value will say and when it should arrive. Based on these assumptions, it generates a second STC value. Your DMP repeats this process each subsequent time that it finds a PTS value. It only ever discards a generated STC value when it learns that one of its assumptions was wrong.

Understand Why PTS-STC Discrepencies Flood the Buffer and Cause Latency

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.

Guidelines

Limit and Reduce Latency

Limit and Reduce Latency

You can reduce the risk of latency and limit its effects. Simply configure the originating encoder to:

Use I frames and P frames only. It should not use B frames.

Minimize the interleave time for audio and video.

Workflows

Workflow to Play Assets from the Memory Card

Workflow to Play Assets from the Memory Card

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.

Procedures

Configure Settings

Play Media

Configure Settings

Adjust Jitter Buffer Control (Advanced Multicast) Settings

Turn Full-Screen Video Mode On or Off

Adjust Jitter Buffer Control (Advanced Multicast) Settings


Note DMPs do not support multicast streaming over Wi-Fi.


You can control how your DMP synchronizes audio with video in a multicast stream.

Procedure


Step 1 Depending on your DMP model and its firmware version, do one of the following.

Click Advanced Multicast in the Settings list.

Click Video in the Settings list.

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.


Related Topics

UI Reference: Elements to Define Jitter Buffer (Advanced Multicast) Settings

Turn Full-Screen Video Mode On or Off

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.


Related Topics

 Watch or Stop Video from a UDP Multicast Stream.

Watch or Stop Video from an HTTP URL.

Watch or Stop Video from a File Stored on Your DMP.

Play Media

Play Assets from a USB Flash Drive

Watch or Stop Video from a UDP Multicast Stream

Watch or Stop Video from an HTTP URL

Watch or Stop Video from a File Stored on Your DMP

Play Assets from a USB Flash Drive

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.

Procedure


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 3 Play the media files.

Step 4 Stop. You have completed this procedure


Related Topics

Watch or Stop Video from a File Stored on Your DMP

Watch or Stop Video from a UDP Multicast Stream

You can start or stop playback of video from a UDP multicast stream.

Procedure


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.

Click Start to play the stream.

Click Stop to exit the stream.

Step 4 Stop. You have completed this procedure.


Related Topics

UI Reference: Elements to Define Video Multicast Settings

Watch or Stop Video from an HTTP URL

To show on your DMP display the video content from an HTTP URL, or to stop showing that video content, do the following.

Procedure


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.

Click Start to play the video.

Click Stop to exit the video.

There might be a delay of as long as 3 seconds.

Step 4 Stop. You have completed this procedure.


Related Topics

UI Reference: Elements to Define Video URLs

Watch or Stop Video from a File Stored on Your DMP

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.

Procedure


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.

Click Start to play the video.

Click Stop to exit the video.

Step 4 Stop. You have completed this procedure.


Related Topics

UI Reference: Elements to Play Locally Stored Video

Reference

UI Reference Topics

UI Reference Topics

UI Reference: Elements to Define Video Multicast Settings

UI Reference: Elements to Define Video URLs

UI Reference: Elements to Play Locally Stored Video

UI Reference: Elements to Define Jitter Buffer (Advanced Multicast) Settings

UI Reference: Elements to Define Video Multicast Settings

Table 14-1 Elements on the Video Multicast Page 

Element
Description

Video Multicast

Multicast Group IP Address

The DNS-routable IP address:

To which the encoder or streaming server must send content.

From which all client systems will receive the UDP multicast stream.

Note DMPs do not support multicast streaming over Wi-Fi.

Port Number

The logical port on your DMP that receives the stream.


Related Topics

Watch or Stop Video from a UDP Multicast Stream

UI Reference: Elements to Define Video URLs

Table 14-2 Elements on the Video URL Page 

Element
Description

Video URL

URL

Use ISO/IEC-8859 (Latin-1) character encoding to specify the HTTP URL. This includes:

The server's routable IP address or DNS-resolvable hostname.

The full pathname, which points exactly to the video file on the server.

 

Note The entire URL must contain fewer than 254 characters. It must not contain any spaces.

Tip When the HTTP service runs on a nonstandard logical port, use the typical method ( :8 08 0, for example) to include a port number in the URL.

UI Reference: Elements to Play Locally Stored Video

Table 14-3 Elements on the Play Video File Stored Locally Page 

Element
Description

Play Video File Stored Locally

Local Storage Path

The local path to the video file.

Did you store the asset on the Secure Digital (SD) flash drive inside your DMP?
Start the pathname with /tmp/ftproot/usb_1/.

Did you store the asset on an external USB drive that is attached to your DMP?
Start the pathname with /tmp/ftproot/usb_2/.


Related Topics

Watch or Stop Video from a File Stored on Your DMP

UI Reference: Elements to Define Jitter Buffer (Advanced Multicast) Settings

Table 14-4 Elements on the Advanced Multicast Page 

Element
Description

When the DMPDM navigation path on your DMP is Settings > Advanced Multicast

Enable Automatic STC Adjustment

Indicates whether STC adjustment is automated.

Jitter Drifting

Indicates the rate of drift, as measured in 50-millisecond increments. Choose an option from the list. Options range incrementally from exactly 50 ms to exactly 1500 ms, after which the one additional option is > 1500 ms. The factory-default value is 1500 ms.

50 ms is the best possible condition.

Multicast Pre-buffer Time (0-2200)

Counts in milliseconds how long the pre-buffer should endure, per PTS. Enter 0 (zero) to use no pre-buffer.


When the DMPDM navigation path on your DMP is Settings > Video

Low Mark of (PTS-STC) (ms)

Media playback duration (in milliseconds) that specifies the smallest permissible buffer size. This value and the High Mark value define the low and high thresholds, respectively, for your DMP's jitter buffer. The actual buffer size might reach either extreme but is more likely to straddle a midpoint.

Except when nothing at all is buffered, this is the least amount of media that will buffer en route to its decoding. Buffer size is proportionate to latency, so a larger buffer proportionately improves the capacity for jitter control.

Whenever your presentation system is one tile in a video wall — or feeds signals to other tiles via RS-232 daisy-chaining — this value should be within 100 ms of the High Mark value. Otherwise, the tiles in your video wall might fall out of sync.

High Mark of (PTS-STC) (ms)

Media playback duration (in milliseconds) that specifies the largest permissible buffer size. This value and the Low Mark value define the high and low thresholds, respectively, for your DMP's jitter buffer. The actual buffer size might reach either extreme but is more likely to straddle a midpoint.

The buffer will never hold any more media than this. Buffer size is proportionate to latency, so a larger buffer proportionately improves the capacity for jitter control.

Whenever your presentation system is one tile in a video wall — or feeds signals to other tiles via RS-232 daisy-chaining — this value should be within 100 ms of the Low Mark value. Otherwise, the tiles in your video wall might fall out of sync.

Time of Calculating Average (PTS-STC) (sec)

Interval (in seconds) that your DMP reserves to calculate the average size of its own jitter buffer and adjust the STC, as needed to alter the data size.

In most case, 60 seconds works well.

Statistics of (PTS-STC)

Click Display to view information about your DMP's jitter buffer.