SRT "No Nulls" Profiles - How and When To Use Them

New in the SRT-OUT-Caller-Solo destination type, are two profiles that are both labeled as "No Nulls" - one for H.264 and one for HEVC (H.265).

What No Nulls Means

Profiles in the SRT-Out-Caller-Solo destination type deliver a Constant Mux Rate MPEG-TS stream. However, the video stream generated by the Solo is variable bitrate. In order to make the mux rate constant, the difference between the bitrate of the Solo's stream and the target mux rate is filled with so-called "null data", also called padding data.

Why would this be important? Some services expect to be able to find certain header information in the Transport Stream multiplex at the same intervals, on a time scale. This type of clocking is defined by the standard TR 101 290/ETSI 290, though some devices may expect constant intervals between the headers, even without being "290 compliant". This null padding is very important for hardware receivers/decoders, and some software-based systems too.

No Nulls simply forwards the stream from the Solo, without adding ETSI 290 padding data. Neither modes use more or less bandwidth from your Solo unit to the cloud, because that path is sent as LRT which never uses a constant mux rate.

When To Use Each

Just to summarize the section above:

Use the "No Nulls" Profile: when you are streaming to a software platform that doesn't expect a constant mux rate.  In-particular, use these profiles any time you are streaming to IRLToolkit or to Psynaps, where they rely on incoming bitrate to measure stream health.  If more services are identified that benefit from these profiles, we will add them here.

Use the other profiles (that use constant mux rate): whenever you are going to a hardware receiver or decoder.  

How To Use The Profiles

Using the profiles is straightforward, just select this as your your Profile in the dropdown. 

To Make An SRT Destination with the No Nulls Profile:

1. Click the "Select New Destination" option on the Dashboard
2. From the list of destination types, select SRT-OUT-Caller-Solo 
3. On the SRT setup page, Select either H.264 or H.265 as your codec type 
4. From the Profiles dropdown, select the 1080p50/60 H.265 No Nulls profile (or the H.264 version if you need H.264 instead)
5. Complete the rest of the parameters such as the SRT url, port, stream key, and passphrase (if required) 

If you do not actually need 1080p and want something lower - you can use Advanced Profile to override the profile, but by still using the "No Nulls" version you will get the variable mux rate stream.

If you already have an SRT destination made, you can also choose to just edit it and change the profile in use.

Now save your destination and start streaming!