- Posts: 32
- Joined: Wed Aug 23, 2017 10:31 am
I recently purchased a Web Presenter HD to reduce the workload on our OBS-based live broadcast computer. Everything is done in 1080p and, depending on the available internet upload speed at the venue, downscaled to 720p. The computer has a Decklink Mini Monitor 4K. To further reduce the workload on the computer, I would prefer the Web Presenter HD to do the downscaling.
Scaling Issues
The scaling issues when down converting 1080p to 720p with the Web Presenter HD are as follows:
> Downwards vertical shifting of downscaled image
> Missing/Reduced image definiton.
Note:
I recommend downloading the images below.
In the image below Ecoding 1 and 7 are identical.
From the image below you can see that, Encoding 1 (and 7) was originated from a 1080p OBS Base (Canvas) then Output (Scaled) out of OBS as a 1080p image fed to the DeckLink card which fed a 1080p50 SDI signal to the Web Presenter HD which downscaled this input streamed it as 720p30. The resulting stream image can be seen in the stream captures 1 and 7.
In the image above, Encodings 5 and 6 were done within OBS. The only difference is that with Encoding 5 the downscaling to 720p was done at the Streaming encoder stage, where Encoder 6 the scaling was done at the Output (Scaled) output.
You will notice that the horizontal lines at the bottom of the image are all visible in the OBS encodings, and barely defined or completely absent in the Web Presenter HD encodings 1,2,3,4, and 7. Web Presenter HD Encoding 3 had some help from OBS as the video was downscaled within OBS to 720p then output via the Decklink Mini Monitor 4K as 1080p and then downscaled and stream as 720p by the Web Presenter HD.
Clearly the Web Presenter HD is using a less computationally intense scaling algorithm, like nearest neighbour, compared to OBS which uses the Lanczos scaling algorithm.
You will also notice in the above image how the Web Presenter HD has shifted the video image down (probably due to the the scaling algorithm used) when the input (1080p) requires downscaling (720p). This can be seen in encodings 1 (7) and 3 especially towards the bottom of the image where the dark graphic ends.
Horizontal Line Scaling
Original image - 1920x1080, Line 1 - Black, Line 2 - White, Line 3 - Black, ...
XML Formatting
The Web Presenter HD comes with no documentation on the formatting of the streaming XML file that can be imported into the Web Presenter HD. The only way to find out more on what <tags> are available is to download 1.4GB of ATEM software updates, extract them and look for the example streaming XML document. Even then, not all options are documented, for example, the only way I found how to add a streaming key to the XML file was to look at the "Here to Record" YouTube video entitled "ATEM Streaming Bridge - What can it do // Show and Tell Ep.74" where, at 3m44s for just 1 second, you can see how to format a stream key into an XML file! Thanks John!
Bugs
If you create a streaming XML where the stream key is undefined e.g. <key></key> and then attempt to upload this XML to the Web Presenter HD you will be unable to change Platforms from either the device interface or through the Web Presenter setup software. You will have to reset the device by either cycling the power or entering the Shutdown Block reboot command.
The Input View on the Web Presenter HD's Monitor Out does not display the full video input and has the right hand side and bottom of the video cropped off if the video input is 1080p.
Audio Meters
Only VU and PPM? Where's the "more", as in "You can even change the type of audio meter from VU, PPM and more!" from your product page? Why no LUFS loudness meters? Almost every streaming platform has loudness requirements, not to mention TV stations. If audio should be correct before entering the Web Presenter HD, then why even have audio meters? Confidence metering in case you hit digital zero?
Questions
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add better (Teranex grade) scaling algorithms?
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add more (modern) streaming transport protocols like SRT (Secure Reliable Transport) and RIST (Reliable Internet Stream Transport) protocols?
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add more user adjustable options to the H.264 encoder e.g. max/min bitrates, intra-refresh, packing the bitstream (x264 --nal-hrd)?
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add loudness audio metering (LUFS)?
> Where is the full documentation on the streaming XML format? What exactly does the <low-latency/> tag do and which platforms support it?
Right now I am seriously contemplating returning the Web Presenter HD and spending the same amount of money on a compact computer, a DeckLink Mini Recorder 4K, and OBS... at least I'll be guaranteed better downscaling, more/modern connection protocols, and more flexibility with the encoder.
Please help me change my mind and get me to keep the Web Presenter HD!
Scaling Issues
The scaling issues when down converting 1080p to 720p with the Web Presenter HD are as follows:
> Downwards vertical shifting of downscaled image
> Missing/Reduced image definiton.
Note:
I recommend downloading the images below.
In the image below Ecoding 1 and 7 are identical.
From the image below you can see that, Encoding 1 (and 7) was originated from a 1080p OBS Base (Canvas) then Output (Scaled) out of OBS as a 1080p image fed to the DeckLink card which fed a 1080p50 SDI signal to the Web Presenter HD which downscaled this input streamed it as 720p30. The resulting stream image can be seen in the stream captures 1 and 7.
- Web Presenter HD vs OBS Scaling - Side-by-Side.png (676.9 KiB) Viewed 6957 times
In the image above, Encodings 5 and 6 were done within OBS. The only difference is that with Encoding 5 the downscaling to 720p was done at the Streaming encoder stage, where Encoder 6 the scaling was done at the Output (Scaled) output.
You will notice that the horizontal lines at the bottom of the image are all visible in the OBS encodings, and barely defined or completely absent in the Web Presenter HD encodings 1,2,3,4, and 7. Web Presenter HD Encoding 3 had some help from OBS as the video was downscaled within OBS to 720p then output via the Decklink Mini Monitor 4K as 1080p and then downscaled and stream as 720p by the Web Presenter HD.
Clearly the Web Presenter HD is using a less computationally intense scaling algorithm, like nearest neighbour, compared to OBS which uses the Lanczos scaling algorithm.
You will also notice in the above image how the Web Presenter HD has shifted the video image down (probably due to the the scaling algorithm used) when the input (1080p) requires downscaling (720p). This can be seen in encodings 1 (7) and 3 especially towards the bottom of the image where the dark graphic ends.
Horizontal Line Scaling
- Web Presenter HD vs OBS Scaling - Horizontal Lines - Side-by-Side.png (41.87 KiB) Viewed 6957 times
XML Formatting
The Web Presenter HD comes with no documentation on the formatting of the streaming XML file that can be imported into the Web Presenter HD. The only way to find out more on what <tags> are available is to download 1.4GB of ATEM software updates, extract them and look for the example streaming XML document. Even then, not all options are documented, for example, the only way I found how to add a streaming key to the XML file was to look at the "Here to Record" YouTube video entitled "ATEM Streaming Bridge - What can it do // Show and Tell Ep.74" where, at 3m44s for just 1 second, you can see how to format a stream key into an XML file! Thanks John!
Bugs
If you create a streaming XML where the stream key is undefined e.g. <key></key> and then attempt to upload this XML to the Web Presenter HD you will be unable to change Platforms from either the device interface or through the Web Presenter setup software. You will have to reset the device by either cycling the power or entering the Shutdown Block reboot command.
The Input View on the Web Presenter HD's Monitor Out does not display the full video input and has the right hand side and bottom of the video cropped off if the video input is 1080p.
Audio Meters
Only VU and PPM? Where's the "more", as in "You can even change the type of audio meter from VU, PPM and more!" from your product page? Why no LUFS loudness meters? Almost every streaming platform has loudness requirements, not to mention TV stations. If audio should be correct before entering the Web Presenter HD, then why even have audio meters? Confidence metering in case you hit digital zero?
Questions
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add better (Teranex grade) scaling algorithms?
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add more (modern) streaming transport protocols like SRT (Secure Reliable Transport) and RIST (Reliable Internet Stream Transport) protocols?
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add more user adjustable options to the H.264 encoder e.g. max/min bitrates, intra-refresh, packing the bitstream (x264 --nal-hrd)?
> Are Blackmagic going to release a fix/patch/update for the Web Presenter HD that will add loudness audio metering (LUFS)?
> Where is the full documentation on the streaming XML format? What exactly does the <low-latency/> tag do and which platforms support it?
Right now I am seriously contemplating returning the Web Presenter HD and spending the same amount of money on a compact computer, a DeckLink Mini Recorder 4K, and OBS... at least I'll be guaranteed better downscaling, more/modern connection protocols, and more flexibility with the encoder.
Please help me change my mind and get me to keep the Web Presenter HD!