Web Presenter HD - Scaling and Other Issues

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Andrew Gibb

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Web Presenter HD - Scaling and Other Issues

PostSun Aug 15, 2021 3:14 pm

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.

Web Presenter HD vs OBS Scaling - Side-by-Side.png
Web Presenter HD vs OBS Scaling - Side-by-Side.png (676.9 KiB) Viewed 3980 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
Web Presenter HD vs OBS Scaling - Horizontal Lines - Side-by-Side.png (41.87 KiB) Viewed 3980 times
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!
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostWed Aug 18, 2021 2:07 pm

I have done further tests with the Web Presenter HD and have discovered that image manipulation occurs even when scaling is not involved.

In the following, a 720p grid (original file attached) was played out of both Adobe Premiere and Media Express with the same results. The resulting output stream from the Web Presenter HD looks as follows.

1x1px Grid - Red Border 720p.png
1x1px Grid - Red Border 720p.png (6.72 KiB) Viewed 3941 times
Original 1x1px Grid with Red Border at 1280x720

1x1px Grid - Red Border 720 Streamed from WPHD.png
1x1px Grid - Red Border 720 Streamed from WPHD.png (13.28 KiB) Viewed 3941 times
Output stream of the 1x1px Grid with Red Border at 720p

As you can see there is no defined grid in the output stream. In the output, the 2nd video line of the original grid is duplicated twice and then every horizontal line has disappeared! The front display of the Web Presenter HD shows the grid as it should be, the monitor out shows a poorly scaled version of the grid, but it's the stream output that looks nothing like the original grid.

To replicate this, download the original 720p grid file and play it into the Web Presenter HD with the stream output matching the input of 720p.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostWed Aug 18, 2021 2:15 pm

The duplication of the 1st or 2nd video line also occurs on 1080p video. With 50p video the 1st video line is duplicated and with 25p video the 2nd video line is duplicated.

1x1px Grid - Red Border 1080p.png
1x1px Grid - Red Border 1080p.png (12.44 KiB) Viewed 3937 times
Original 1x1px Grid - Red Border 1080p


1x1px Grid - Red Border 1080p50 streamed from WPHD.png
1x1px Grid - Red Border 1080p50 streamed from WPHD.png (515.11 KiB) Viewed 3937 times
1x1px Grid - Red Border 1080p streamed at 1080p50 - 1st line duplicated


1x1px Grid - Red Border 1080p25 streamed from WPHD.png
1x1px Grid - Red Border 1080p25 streamed from WPHD.png (520.25 KiB) Viewed 3937 times
1x1px Grid - Red Border 1080p streamed at 1080p25 - 2nd line duplicated

If someone with a Web Presenter HD could test to verify my findings that would be extremely helpful.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostFri Aug 20, 2021 8:57 am

I have done another test showing how the video lines are being manipulated by the Web Presenter HD when fed a 720p50 source which is then streamed at 720p50.

Since I am unable to upload .MP4 video files I have hosted a ZIP file at the following location:

https://slambang.co.za/Moving_Lines_Video_Tests.zip (7.5MB)
(The link will remain up as long as the scaling issue persists with the Web Presenter HD)

Once extracted you should see a folder Moving Lines Video Tests


Within the Moving Lines Video Tests\720p50 folder
The original files used for testing 720p video:
    01 Moving Single Pixel Lines 720p50 - Test Video.mov (Apple ProRes LT)
    01 Moving Single Pixel Lines 720p50 - Test Video.mp4
The Web Presenter HD 720p Output Stream based on the test files above:
    02 WPHD Moving Single Pixel Lines 720p50 - Web Presenter Output Stream.mp4
The OBS 720p Output Stream based on the test files above:
    03 OBS Moving Single Pixel Lines 720p50 - OBS Output Stream.mp4


Within the Moving Lines Video Tests\1080p50 folder
The original files used for testing 1080p video:
    01 Moving Single Pixel Lines 1080p50 - Test Video.mov (Apple ProRes LT)
    01 Moving Single Pixel Lines 1080p50 - Test Video.mp4
The Web Presenter HD 1080p Output Stream based on the test files above:
    02 WPHD Moving Single Pixel Lines 1080p50 to 720p50 - Web Presenter Output Stream.mp4
The OBS 1080p Output Stream based on the test files above:
    03 OBS Moving Single Pixel Lines 1080p50 to 720p50 - OBS Output Stream.mp4

NOTE:
You will notice that the OBS Output Stream files are much larger than those produced by the Web Presenter HD. This is because the Web Presenter HD was set to the HyperDeck High profile and the unit chose 1.7Mbps (VBR?) as the appropriate bitrate for the material being encoded. OBS was set to 10Mbps CBR. The test wasn't to evaluate the encoding efficiency but image scaling quality.

Please test with your Web Presenter HD unit and please let me know if I am testing incorrectly.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostTue Aug 24, 2021 12:31 pm

Yes, even more tests! This time to show the aliasing artefacts introduced in 720p to 720p, and 1080p to 720p output streams.

The Rotating Lines Test - A white rotating line with red borders on the edge of the video frame.

Although there are no aliasing artefacts introduced in the 1080p to 1080p there are, as with all 1080p and 720p output streams, duplicates of the first video line of the input video onto the first 2 video lines of the output stream i.e. input video line 0 = output stream video lines 0 & 1. This means that the last video line of any 1080p or 720p input will be lost.

The Top Lines Test - A white line moves every 10 frames from video line 0, line 1, line 2, and then back up and off the screen. A white border is also present on the edge of the video frame. You might have to zoom up on the output video streams to see exactly what's happening. Also note how the last video line is absent from the output streams.

I have hosted both the Rotating Lines and Top Lines Tests and can be downloaded by clicking the following link:-
https://slambang.co.za/Rotating_Lines_and_Top_Lines_Tests.zip (171MB)
(The link will remain up as long as the scaling issue persists with the Web Presenter HD)

I started to think that perhaps this is the way the Web Presenter HD was supposed to handle downscaling/down converting so I had a look at the launch video and the product pages:

Web Presenter Launch Video - Grant Petty (40m21s).png
Web Presenter Launch Video - Grant Petty (40m21s).png (450.92 KiB) Viewed 3692 times


Blackmagic Web Presenter - Teranex Conversion Technology on the SDI input.png
Blackmagic Web Presenter - Teranex Conversion Technology on the SDI input.png (11.02 KiB) Viewed 3692 times
https://www.blackmagicdesign.com/products/blackmagicwebpresenter

Clearly, from the statements above, the Web Presenter HD should be producing better quality images. Either that or the Decklink Mini Monitor 4K, that is feeding the signal to the Web Presenter HD, is at fault...?

Any user or support team (yes, I have a ticket) feedback regarding the issues mentioned above would be greatly appreciated.
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Roman Pytkin Pekarek

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Re: Web Presenter HD - Scaling and Other Issues

PostTue Aug 24, 2021 11:14 pm

Im streaming about 10 years .. I was tested lot of SW and HW encoders .. But in last years i was builded small intel nuc with obs into all my video racks .. Quality of X264 is the best for me ..
http://tally.pytkin.sk
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostFri Aug 27, 2021 6:43 am

Roman, I'm starting to think that perhaps the best encoding/streaming solution would have been a self-built one, like you've done. It would have cost about the same as a Web Presenter HD and would have been more flexible in terms of communication protocols (not just RTMP), codecs, and scaling.

While I am waiting for Support to get back to me, if anyone with a Web Presenter HD could please tell me if they've also experienced (or not) any scaling or other issues as mentioned above.
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r.mens

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Re: Web Presenter HD - Scaling and Other Issues

PostFri Aug 27, 2021 5:19 pm

Wondering about the supported XML tags too. Couldn't find any documentation and had to figure out how to craft an XML file myself. I understand that the Web Presenter HD is a fairly new product, but an update would be nice.
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jt1972

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Re: Web Presenter HD - Scaling and Other Issues

PostMon Aug 30, 2021 3:03 pm

Just purchased Web Presenter HD and was a little - well to be honest, very disappointed about the video quality it produced with the highest quality to YouTube.

Better encoding and scaling quality, please.

And selectable and adjustable Sharpen function would be nice :)

And yes, please add the XML documentantion ASAP.
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Roman Pytkin Pekarek

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Re: Web Presenter HD - Scaling and Other Issues

PostMon Aug 30, 2021 10:38 pm

Highest quality is bad ?
http://tally.pytkin.sk
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jt1972

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Re: Web Presenter HD - Scaling and Other Issues

PostWed Sep 01, 2021 9:07 am

Tried upscaling from 720P50 to 1080P50 and it should do it better.

Feature request:
Export the current selected settings as XML. This would allow to tweak the settings easily.
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Johannes Jonsson

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Re: Web Presenter HD - Scaling and Other Issues

PostFri Sep 03, 2021 1:06 pm

jt1972 wrote:Tried upscaling from 720P50 to 1080P50 and it should do it better.

Feature request:
Export the current selected settings as XML. This would allow to tweak the settings easily.


Well by upscaling from 720 to 1080 you only get 720 resolusion and quality image in a 1080 resolusion frame.
Johannes
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jt1972

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Re: Web Presenter HD - Scaling and Other Issues

PostMon Sep 06, 2021 4:53 pm

Johannes Jonsson wrote:Well by upscaling from 720 to 1080 you only get 720 resolusion and quality image in a 1080 resolusion frame.


Yes, but the upscalig can be done better.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostThu Sep 16, 2021 2:31 pm

Has anyone with a Web Presenter HD managed to replicate the scaling issues as mentioned above or noticed any introduced aliasing when feeding the unit a 720p signal?

It's been over a month since I first mentioned this potential issue and nobody on the forum has mentioned experiencing the scaling/aliasing issue. I'm starting to think that it's just my unit that has the issue.

I would be extremely grateful if someone could confirm that they have tested the unit with the test files (see links above) and either do or don't see the scaling and duplicate 1st video line issues that I've experienced.

Blackmagic's support department said that they have passed my feedback onto the Developers who don't usually make comments on issues to customers.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostThu Apr 21, 2022 12:38 pm

With the release of the Blackmagic Web Presenter 3.1 Update I thought I'd report back on my findings.

None of the issues mentioned above have been resolved.

It's very disappointing that one of the selling points, namely having Teranex conversion technology, has not been fixed/implemented a year after its release. So much for the "incredibly clean looking video" mentioned on the Web Presenter product page. I'm surprised that everyone else who's purchased the Web Presenter HD/4K is seemingly happy with the issues mentioned above.

Oh well! It's back in its box and on the shelf again. Completely Unusable.
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Re: Web Presenter HD - Scaling and Other Issues

PostThu Apr 21, 2022 4:51 pm

Andrew:

First let me preface that you are far more advanced than I and that it is unfortunate that your experience with the product was unsatisfactory. My issue is far more pedestrian and I hope you can get me on the right track.

I bring video into OBS from a canon PTZ camera via NDI and another computer via NDI and audio in via usb from a Focusrite 18i20 audio interface. Both the video and audio feeds successfully into OBS.

Both video and audio (post effects and sync delay) SHOULD go from OSB to the Web Presenter 4K via a projector to an HDMI out on my laptop to a BMD HDMI to SDI converter. The computer and Web Presenter are not connected by USB.

For OSB I have my mic/aux global device set as channels 1 and 2 of my Focusrite (the Focusrite send 3 mono and 2 stereo feeds back to outs 1 and 2) and my desktop audio global device set as the Web Presenter. I have tried projecting both the preview and program feed with no difference. I have tried running virtual camera and not with no difference.

On the audio meters, I see input on the mic/aux (something is coming in) but nothing on the desktop audio (nothing is going out). If I turn monitor on a sound channel and set the monitor device as the Web Presenter, I get audio to the web presenter, but it is pre effects and without sync delay. If I send test audio from Windows to the Web Presenter I get audio to the web presenter. So I conclude that audio may be delivered successfully from the HDMI port to the Web Presenter, but OBS is not sending any audio their, at least not from the program feed.

What am I missing here?

Thanks in advance, take care, and stay safe,

Brian


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Xtreemtec

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Re: Web Presenter HD - Scaling and Other Issues

PostFri Apr 22, 2022 9:54 am

Did they mention what is changed in 3.1?
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostFri Apr 22, 2022 1:54 pm

From the Blackmagic Design Support Center:

What's new in Blackmagic Web Presenter 3.1
New features and fixes for Web Presenter 4K and Web Presenter HD
* Add support for tally light, talkback and remote control of supported Blackmagic Design cameras.
* Add support to allow configurable DNS servers when set to static IP mode.
* Ensure audio-visual sync is maintained if SDI input is disconnected then reconnected.
* Add new streaming platform presets.
* Ensure data indicators display correctly.
* General performance and stability improvements.


As always, the vague "General performance and stability improvements". In typical Blackmagic Design fashion they fixed something and did not listing the fix in the release notes - the encoding glitch (https://forum.blackmagicdesign.com/viewtopic.php?f=4&t=139374) seems to be fixed but wasn't mentioned in their "release notes".

I guess, like the encoding glitch, I'll also have to wait a year (August 2022) before Blackmagic Design finally fix the scaling issues.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostMon Aug 08, 2022 10:15 am

Calling all Web Presenter HD and 4K users - I need your help. I need people to test their systems to see whether they are experiencing the same issues as I am.

For testing on YouTube download the following file (contains 30fps and 60fps tests):
https://slambang.co.za/Blackmagic_Web_Presenter_HD-4K_30fps_and_60fps_Test_Files.zip (117MB)

For testing on platforms that support 50fps live streams that don't alter the source frame rate (i.e. not YouTube live streams) download the follwing 2 zip files:
https://slambang.co.za/Moving_Lines_Video_Tests.zip (7.5MB)
https://slambang.co.za/Rotating_Lines_and_Top_Lines_Tests.zip (171MB)

Load the files into your system and play them into your Web Presenter HD or 4K and stream them at both 720p and 1080p to a private YouTube stream and see if the results on the YouTube stream look anything like I've described above. In other words, do you see any downscaling artefacts like jagged edges, missing, ill-defined or flickering lines similar to my results that I have included in the zip files.

Neither Blackmagic Design's support or developers have been able to tell me if they've replicated my scaling issues. I'm hoping that users of the Web Presenter HD or 4K can help me confirm the issue that I'm experiencing.

According to the promotional material and Grant Petty, the "Blackmagic Web Presenter features Teranex conversion technology on the SDI input for incredibly clean looking video" and "it just works".

Your efforts in testing the streaming output will be greatly appreciated.
Last edited by Andrew Gibb on Wed Aug 10, 2022 2:01 pm, edited 1 time in total.
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floh79

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Re: Web Presenter HD - Scaling and Other Issues

PostMon Aug 08, 2022 10:54 am

Hi, I’m camping but I could test next week. So I’m “subscribing” this thread. I have Webpresenter 4K.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostWed Aug 10, 2022 2:10 pm

Use these files if testing on YouTube!!!

Since mid-2020 YouTube stopped streaming live video at the source frame rate and now converts 25fps and 50fps to 30fps by duplicating or dropping frames. Only 30fps or 60fps live video sources will remain unaltered. This means that my initial test video downloads, which are all at 50fps, will produce dropped frames when live stream testing on YouTube!

Please download the following 30fps and 60fps video test file when testing on YouTube:
https://slambang.co.za/Blackmagic_Web_Presenter_HD-4K_30fps_and_60fps_Test_Files.zip (117MB)
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostThu Aug 11, 2022 1:54 pm

My results of streaming the 60fps test videos to YouTube can be seen on YouTube:

Web Presenter HD 720p60 to 720p60 Test


Web Presenter HD 1080p60 to 1080p60 Test


Web Presenter HD 1080p60 to 720p60 Test
(downscaling done by the Web Presenter HD)


At first glance, looking at the above streams one might wonder what all the fuss is about but, once you compare these live streams from the Web Presenter HD to the original video file, or even a live stream (not a recording) from OBS, the scaling and line shifting issues with the Web Presenter HD become apparent.

To see a side-by-side comparison of the original video file with the live stream output by the Web Presenter HD and OBS live stream download the following ZIP containing 6x MP4 video files:
https://slambang.co.za/Web_Presenter_HD_-_Side-by-Side_Orginal_vs_Web_Presenter_vs_OBS.zip (410MB)

I highly recommend using a media player that allows you to step forwards and backwards frame-by-frame through the video. For Microsoft Windows I highly recommend the MPV media player (https://mpv.io/)

The scaling and line shifting issues cause aliassing issues as seen in this video:

Michael Morrison - Web Presenter Test5

In the above example, note the jagged lines defining diagonal lines and the jagged edges of the circles and "smudgy" text in the opening titles.

I look forward to your test results.
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Andrew Gibb

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Re: Web Presenter HD - Scaling and Other Issues

PostSun Sep 11, 2022 4:58 pm

To present a more real world example of the scaling and aliasing issue with the Web Presenter HD I have more test footage and results to share with you. In an attempt to preserve these issues in the output stream I encoded side-by-side comparisons as Apple ProRes LT which produced >500MB output files.

mpv-shot0002.jpg
mpv-shot0002.jpg (70.53 KiB) Viewed 163 times

mpv-shot0001.jpg
mpv-shot0001.jpg (284.53 KiB) Viewed 163 times

Things to look out for in the results: moiré patterns (Ravi's shirt), swimming detail (yellow dots), detail that disappears and reappears (Ravi's jacket), and aliasing (Stephanie's hair, circle edges, and titles).

The test source file, encodings from OBS and the Web Presenter HD, and the side-by-side comparisons are all 3 can be downloaded from Dropbox at the following link:

https://www.dropbox.com/s/9ltxpoqcjzu0isq/Web%20Presenter%201080p60%20to%20720p60%20Colour%20Test%203%20Test.zip?dl=0

Please note: The ZIP file containing the aforementioned files is 1.7GB

Once again I'm asking all Web Presenter HD/4K owners to test their systems to see whether they are experiencing the same issues as I am and to report back their findings.

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