Troubleshooting Network

1. My Encoder and Decoder are connected to our LAN. I have a video signal going to the Encoder, but the Decoder says: “No signal received”.
   
   
2. The output quality is poor. The downstream monitor looks green and blocky. Why was the output so much better on the bench?
   
   
3. What can cause a loss of audio-video sync?
   
   
4. Why don’t I see changes made to Encoder settings downstream instantaneously?
   
   
5. When I change the VBR buffer setting to 0, I notice a corrupt frame every ten seconds. What causes that?
   
   
6. After enabling Shuffle, it can sometimes take 60 seconds or more to see the correction downstream. What causes this?
   
   
7. There are new FEC settings in the latest software update. What do they mean?
   
   
8. How can I switch from TCP/IP mode to T1 mode? How can I switch back from T1 mode to TCP/IP mode?
   
   

1. My Encoder and Decoder are connected to our LAN. I have a video signal going to the Encoder, but the Decoder says: “No signal received”.
   The most likely cause of this is that the Internet Protocol (IP) settings for either the Encoder or Decoder are not correct. Since both devices run on the Windows XP Embedded operating system, you will need to make appropriate changes in the Network Connections control panel on both devices.

   Typically, this involves assigning a TCP/IP number, subnet mask, and default gateway on both devices. Once that is done and connectivity is confirmed between the two devices by using the PING utility, you can easily configure the Encoder to stream to the Decoder by clicking on the Network menu and choosing “Change Decoder TCP/IP”.

   Streambox systems normally ship as a DHCP client, so if a DHCP server exists on your network the systems will receive TCP/IP settings automatically. The TCP/IP address for the Decoder will appear on its front LCD panel, and from there you can easily configure the Encoder to stream to the Decoder's TCP/IP address.

   When you purchase a Streambox system, you can tell us to pre-configure the systems with your preferred TCP/IP settings. Please note that we may not be able to completely test these settings in-house.

   Another possibility is that a firewall might be blocking the network connection, or it might be performing Network Address Translation (NAT) which will require port forwarding configuration. Consult your firewall manual to learn how to do this.

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2. The output quality is poor. The downstream monitor looks green and blocky. Why was the output so much better on the bench?
   This type of output shows classic symptoms of extreme packet loss caused by sub-optimal network conditions. Increasing FEC and Shuffle settings usually resolves this problem and gives you the high-quality output Streambox is famous for.

   A good indicator of packet loss is the front LCD panel on the Decoder. You will note two values - L= and R=. L= is a running count of lost frames, and R= is a running count of recovered packets. Typically, L=0 is the goal, while an ever-increasing R= value just means that FEC is set correctly to help recover packets.

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3. What can cause a loss of audio-video sync?
   Making certain adjustments, such as bitrate, buffer length, or FEC percentage, can affect A/V synch for a brief period of time, but this will eventually even out while streaming. One way to counteract this is to stop and restart the Decoder by clicking on “Send Restart” from the Encoder menu.

   Running a Remote Desktop connection during a low-bitrate encoding session could cause temporary audio or video distortion due to a higher CPU load on the Encoder. This condition usually lasts less than ten seconds. Also, operating a Remote Desktop session while encoding at high bitrates has been known to cause a temporary loss of audio-video synch.

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4. Why don’t I see changes made to Encoder settings downstream instantaneously?
   As with most codecs, the Streambox® ACT-L3™ codec uses temporal compression with index frames (called "I-frames"), which send an uncompressed frame at specific intervals. The frames between I-frames are called delta frames. The Encoder will send an I-frame followed by ten seconds (by default) of delta frames before sending the next I-frame. If an adjustment is made between I-frames, it does not usually propagate downstream until the next I-frame is sent from the Encoder.

   Users may adjust the I-frame interval through the Encoder application. This phenomenon can also happen when buffering is enabled and latency is high.

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5. When I change the VBR buffer setting to 0, I notice a corrupt frame every ten seconds. What causes that?
   This is known by using this setting at lower bitrates. When you set VBR=0, you are essentially changing it to Constant Bit Rate (CBR). If the bitrate is set too low, the buffer length is insufficient to hold a complete I-frame, so only a partial I-frame is rendered.
   
   

   To improve the rendering, you will need to increase the bitrate using one of the following methods:

   • reducing encoding resolution
   • decreasing audio bitrate
   • increasing latency (to 0.3 or 0.2 sec)
   • turning off shuffle or reducing FEC rate

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6. After enabling Shuffle, it can sometimes take 60 seconds or more to see the correction downstream. What causes this?
   Since the Encoder is basically using Shuffle to rearrange the order in which the data packets and FEC packets are sent, the Decoder may take some time to discard old packets. As a result, the effect may not appear downstream for a longer period than normal.

   This can be alleviated by sending a Restart Decoder command from either the Encoder UI or from the LCD panel on the front of the Encoder.

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7. There are some new FEC settings in the latest software update. What do they mean?
   It's called Burst FEC, and it's a powerful new tool to correct multiple packet loss, whether sequential or random. Burst FEC adds multiple FEC packets to each group of data packets.
   
   In this illustration, we see three data packets and two FEC packets:
   
   If any two of this group of five packets are lost, Burst FEC will be able to recover from the loss. Burst FEC can recover from multiple packet loss up to the number of the FEC packets per sequence selected.

   For example, a setting of 'R-S 64/10' can recover from up to 10 random or sequential packets lost in a group of 74 (64+10) packets. Burst FEC is denoted as “R-S x% (D/F)” in the encoder interface, where D stands for number of data packets, F stands for number of FEC packets, and x% is the percentage of the data stream that will be consumed by Burst FEC.

   Burst FEC can be used with the “Shuffle” mode to increase the length of the burst protection sequence.

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8. How can I switch from TCP/IP mode to T1 mode? How can I switch back from T1 mode to TCP/IP mode?
   This is only available on systems that include the T1 networking option. To switch from T1 to TCP/IP mode:
   
   • From the front panel of the Decoder, switch to TCP/IP mode from the Network menu. You will notice that the stream stops and the LCD will display the Decoder's TCP/IP address and "NO INCOMING DATA". At this stage, this is normal.
   • Attach a VGA monitor, USB keyboard and USB mouse to the Encoder. From the Network menu of the Encoder application, click on "Switch to TCP/IP mode". Note that this now changes the choices you have under the Network menu to reflect TCP/IP options.
   • Click on "Change Decoder TCP/IP address" and change the TCP/IP address to that shown on the front LCD panel of the Decoder.
   • At this point, assuming the TCP/IP address is correct and network connections are sound, the stream should be visible downstream of the Decoder.
   • If the Decoder is at a remote or unattended location where it's not possible to be physically at the console, you may connect using Windows Remote Desktop which requires an Ethernet connection. Once connected, simply exit the Decoder application and restart it using the following command:

     c:\Streambox\transport.exe bbcodec /ip

   To switch from TCP/IP mode to T1 mode:

   • From the front panel of the Decoder, switch to T1 mode from the Network menu. You will notice that the stream stops and the LCD will display "NO INCOMING DATA". This is normal.
   • From the front LCD panel of the Encoder, switch to T1 mode from the Network menu.
   • Assuming the connection is good, you should see a video stream coming from the Decoder.

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