Question about $10 HDMI Recorder

[jimdagys]

I am trying to do some experiments recording/capturing HDMI. It seems difficult to get simple useful information. I found this $10 dongle:
https://www.aliexpress.com/item/4001043540669.html
The user reviews look good, but, I don't know if this dongle will work. You can see that is just plugs into USB port on computer, and has HDMI female port. The whole thing appears the size of ordinary USB thumb drive.
I plan to use this device to connect to HDMI-out on Walmart on-air TV recorder.
https://www.walmart.com/ip/Ematic-AT103B-Digital-Converter-Box-with-LED-Display-and-Re...ities/28505040
This Walmart device has HDMI out (unencrypted) to connect to flat screen TV. Obviously, if I want to record the broadcast TV, I can simply use this Walmart recorder by itself. But I want to test a HDMI recorder that plugs into USB on computer from the HDMI-out on the Walmart device.
So my questions are:
1) Do you think the above dongle will work?
2) Do you have concern/recommendations for other (better?) such dongles that are cheap?
3) For the dongle I have listed above, it seems that no software is included. What kind of GUI software would be used (for start/stop recording, etc)?

[johnnyquid]

I have a similar device. One issue I found is that it only records audio in mono. For the price, I wouldn't expect much.

[Hunk91]

I bought one like this last December (I paid mine 12 Euros on Amazon).

There is a small instruction flyer in it and it says that you may use : OBS Studio, VLC and Amcap.

I did a few tests with it, and the source was my television decoder provided by my internet provider, the output signal was 1920x1080 at 50fps.

I used OBS Studio: capturing in 1920x1080 resulted of a poor frame rate (like 5 or 10 fps). I didn't checked farther inside OBS to adjust it.

I tested with VLC and could capture a video at a PAL DVD resolution (720x576 at 25 fps) without any problem, the result was OK. For HD resolution it showed me a 5 and 10 fps rate.

I tested with VirtualDub2 and got a good 1920x1080 at 25 fps with no frame drop.

I also tested with Arcsoft TotalMedia Studio (which is the software provided with my ezcap stick) and could capture at 720x576 at 25 fps (PAL DVD resolution) but the DAR was 4/3 instead of 16/9. With the help of DVDPatcher I could changed the DAR to 16/9 without reencoding.

Every time when I check for a 1920x1080 resolution the frame rate proposed was 5 to 10 fps.

If you want to capture in HD then go with VirtualDub2.

I have not checked for the audio but It seemed to me that it was stereo (or maybe the mono track is doubled to make stereo).

Please consider that this HDMI USB capture device is a bootleg of the elgato Cam Link 4K HDMI USB capture. But the difference is that the Elgato has a 3.x USB port whereas this one has a USB 2.X port . And the box even says "Conform to USB Video 1.5 and 1.0 standard" (check this for more information : https://en.wikipedia.org/wiki/USB_video_device_class)

Honestly I'm satisfed with this, it's doing the job I was hoping, but keep in mind that a $10 stick will not offer the same quality as a $100 , but for a first approach of HD capture that a good entry point.

Best regards

[Cornucopia]

In terms of this piece of equipment, and especially as regards the HD level approach, I might have some info that could help.

It comes down to bitrates.
If the input is HDMI and the output is USB, the bitrate will still be similar even if the data packeting structure is reorganized.

Simply, 720x576@25fps with 12bits (using 4:2:0) comes out to 119Mbps.
And 1920x1080@25fps also with 12 bits, works out to 593Mbps.

These do not count the necessary audio as well, though that is much smaller.

Since USB 2.0 is 480Mbps and USB 3.0 is 5000Mbps,
It is clear that if one uses an uncompressed USB UVC format, the SD bitrate can be accommodated at the full framerate, but that the HD bitrate cannot - IF the pipeline does not fully support USB 3.0 throughout the pipeline (for example, the port, the device, any hubs, any cabling).

While some webcams or capture devices are capable of using other (compressed) forms of structuring of the signal, allowing the bitrate to be reduced in order to completely cover the requirements of a full framerate signal, others don't havr that capability.

I would look in that direction to fix your issues (better pipeline or more compression, or both).

As far as the original request is concerned, you get what you pay for. And I wouldn't trust any device that costs merely $10 to be a higher performing device.


Scott

[lordsmurf]

$10? I'm in. That'll be fun.

I expect it to be garbage.

This can't be factual: "NO driver required,"

[jagabo]

This can't be factual: "NO driver required,"

It probably appears as a webcam. So the driver is already built into Windows.

[lordsmurf]

Amazon had one of these for $12.
It's on the way.

Sometimes it's fun to test crap, see how awful it is.

[jimdagys]

Ok, I received this $10 HDMI capture dongle in the mail. I downloaded VirtualDub2 and recorded some 1080p TV video that came out of the Ematic TV broadcast On-air device (see above post #1). Some things I don't understand. A 40 second video recorded with the Ematic is about 60MB, and a 40 second video from the HDMI capture dongle is about 182 MB. I can't seem to adjust video bit rate, codec, or audio codec on the HDMI capture dongle. On the "Select video compression" dialogue box, only MJPEG is available and the container is AVI. On the "Select audio compression" dialogue box, I can't choose mp3. Is there a way to reduce the file size directly while capturing, while still maintaining good quality 1080p/29.97fps? I don't want to re-encode the video from the HDMI capture. The Ematic device is convenient because it captures a good quality on-air video that doesn't require any re-encoding. Even worse, the video from the dongle won't play in the Ematic player; apparently the MJPEG codec is not "standard" compared to h264, mpeg, etc. Is there anyway to get the video from the HDMI capture dongle to play in the Ematic player without re-encoding? Also, Lordsmurf, can you look at the below attached video (HDMIcapture1080.avi) and give a critique on quality? To me, the quality looks very good.
See below video samples:

[jagabo]

The Ematic box "downloaded" the MPEG2/AC3 video transport stream that was broadcast by the TV station. That compressed video was decompressed and transmitted as uncompressed video over the HDMI cable (that's the only thing that can travel over HDMI). The HDMI capture device then deinterlaced that video (poorly, discarding one field and resizing what's left) and compressed it with its on-board MJPEG encoder. That MJPEG stream (along wiht PCM audio) was sent over the USB port to the computer. So what's in the AVI file is essentially just a series of JPEG images, 29.97 per second. MJPEG is is much less efficient than MPEG2 as it has no inter-frame compression, no motion vectors, etc. Hence, the larger file size.

From what I've read, the "USB 3" port on the device is really a USB 2 port. USB 2 doesn't have the bandwidth to transmit uncompressed high definition video. But if the device is connected to a USB 2 port try changing to a USB 3 port and see if there is any difference.

[Hunk91]

Hi!

i couldn't use a video codec neither with Vrtualdub2 during the capture. I could do it after by opening the avi video file captured in virtualdub2 and could then encode video to XviD and audio to mp3.

If you want you can try to download AVItoMP4 in order to convert the capture AVI file to x264 for video and aac for audio. This will result in a MP4 or MKV file that should be read on your EMATIC TV BROADCAST player.x264 and aac

You may also try VLC to capture (but you need to set some parameters before such as aspect ratio, bitrates, etc...) and ou will be able to directly capture with x264 and aac codecs and get a MP4 video file.

I managed to create a 720x576 MPEG video file (PAL DVD) with VLC and this dongle, but I think you are looking for a 1920X1080 FULL HD video file.

[jimdagys]

Thanks for the reply. I also read in many places the $10 HDMI capture dongle doesn't support usb3. I also don't have a usb3 computer. You said,

The HDMI capture device then deinterlaced that video (poorly, discarding one field and resizing what's left) and compressed it with its on-board MJPEG encoder.

Does that mean that any capture software (OBS, VLC, Arcsoft ) etc) will yield the same poor result that has the MJPEG codec?
I could possibly borrow a Windows 10 usb3 computer. How can you detect "discarding one field, resizing what's left"? By visual inspection of the video, or by looking at some video parameter?

[jagabo]

You said,

The HDMI capture device then deinterlaced that video (poorly, discarding one field and resizing what's left) and compressed it with its on-board MJPEG encoder.

Does that mean that any capture software (OBS, VLC, Arcsoft ) etc) will yield the same poor result that has the MJPEG codec?

Yes. Though it's possible some capture software will decompress the incoming MJPEG and recompress it with some other codec on the fly.

How can you detect "discarding one field, resizing what's left"? By visual inspection of the video, or by looking at some video parameter?

Visually. Compare the ematic cap on the left to the HDMI cap on the right:


[Attachment 56909 - Click to enlarge]

If you zoom in on the images it's very obvious the HDMI cap is missing every other scan line (4x point enlargement):


[Attachment 56910 - Click to enlarge]

You can see it all all sharp near-horizontal edges. Apply the Deinterlace filter (bob, keep top or bottom) and you'll see exactly the same thing. And this type of deinterlacing leads to jerky playback as it leaves you with a a duplicate frame every 5 frames. It's very easy to see in panning shots.

[jimdagys]

Ok, the simple takeaway to the non-expert appears to be this:
1) HDMI capture device video is more blurry
2) panning shots more jerky
Do you think the $100 El Gato would capture in usb3 port without these problems? What would happen if the El Gato was plugged into usb2 port? Would there be the above problems with the video?

[jagabo]

Are you referring to the similar looking Cam Link device?

https://www.elgato.com/en/gaming/cam-link-4k

I don't know anything about their current devices.

[jimdagys]

Ok, no big deal about the El Gato. Just curious.
One more question about the HDMI capture dongle:
You mentioned about the problem in getting a good quality capture video is related to the limitation of usb2. Then the big question is, how can the Ematic have such a better video quality when it also uses usb2 port for the memory stick that plugs into it?

[jagabo]

You mentioned about the problem in getting a good quality capture video is related to the limitation of usb2. Then the big question is, how can the Ematic have such a better video quality when it also uses usb2 port for the memory stick that plugs into it?

The Ematic device is downloading the over-the-air broadcast. That broadcast is already compressed with MPEG2 and AC3 audio. So your recording is the exact same quality the TV station is broadcasting. That ~12 Mb/s stream is no problem for recording to a USB2 drive.

The HDMI Capture is is receiving uncompressed video over the HDMI port. For a 1080i broadcast that's about 500 Mb/s. Too much for USB2. So it has to be compressed before it's transferred via USB. The capture device uses MJPEG which is very inefficient. So you're losing quality from another round of lossy compression and the device's poor deinterlacer.

[jimdagys]

Thank you for that explanation.
I decided to capture a 1280x720 (instead of 1920x1080) TV broadcast, using the HDMI capture dongle and the Ematic. For some reason, the Ematic capture is at 59.94 fps. I thought that all broadcast TV was at 29.97 fps, so (to be the same fps) I set the HDMI capture dongle to 29.97 fps.
Can you take a look at these two videos? It might be that at 1280x720, there is a smaller difference in quality between the Ematic and the HDMI capture dongle.

[Cornucopia]

(Note that all mention below of 24 or 30 or 60 also includes more common fractional versions 24000/1001 and 30000/1001 and 60000/1001)

In US, currently:
Broadcast TV can be...For SD, interlaced or progressive 24, 30, 60 Fps.For 720, it can be progressive 24, 30, 60. For 1080, it can be 24, 30 interlaced or progressive, or can be 60 interlaced. 1080 or above cannot be 60p or above until ATSC 3.0 arrives.

Scott

[jagabo]

I decided to capture a 1280x720 (instead of 1920x1080) TV broadcast, using the HDMI capture dongle and the Ematic. For some reason, the Ematic capture is at 59.94 fps. I thought that all broadcast TV was at 29.97 fps, so (to be the same fps) I set the HDMI capture dongle to 29.97 fps.

1080i at 29.97 fps delivers 59.94 different half pictures per second. If you're downscaling that to 720p it should be captured at 59.4 frames per second to retain smooth motion. 1280x720 is broadcast at 59.94 frames per second.

[jagabo]

I believe the North American OTA broadcasters use mostly 1080i at 29.97 fps or 720p 59.94 fps on their primary channels.

[jimdagys]

Jagabo,
What was your precise method to get snapshots and enlarging to post the CBS logo? I know VLC takes snapshots, but absolute clarity is a must here, and different methods yield different results. For example, when you are playing the video, do you pause it, and then take the
the snapshot, or do you take the snapshot as the video is playing?

[jagabo]

I opened the videos in VirtualDub2, copied the desired frame to the Clipboard buffer (Video -> Copy Source Frame To Clipboard), then pasted that as a new image in an image editor (a very old copy of PhotoImpact). But you could do it in an AviSynth script too:

v1 = LWLibavVideoSource("Ematic1080.mts")
v2 = LWLibavVideoSource("HDMIcapture1080.avi").ConvertToYV12()

v1 = v1.Crop(1596,896, 140, 140) # just the logo
v2 = v2.Crop(1596,896, 140, 140) # just the logo

StackHorizontal(v1, v2)
# PointResize(width*4, height*4) # enable this line if you want a 4x enlargement

[jimdagys]

I used VirtualDub2 with the HDMI capture dongle. This produced a result way better than OBS. The problem is: On four computers, two Windows 7 and two Windows 10, only one computer (Windows 7) could I get the video/audio to display in VirtualDub2. The other three computers, when I start VirtualDub2, the software comes up, but when I click Capture>Capture AVI, there is only a blank screen, no video or audio. And therefore, I'm not able to record any video.
My question is, why is this, and how can I get the other three computers to display the video/audio when I click Capture AVI?
For the record, when I used OBS, motion in the captured video was very jerky. I tried all presets with the same result. Except when I used "lossless", that produced a video that was 900MB/minute and the codec was ut. VLC would not play (unsupported), but MPC-HC played it. After using Vidcoder, I was able to recode to H264, to about 30MB and the video played well.
But Virtual Dub2 captured the video very good, all in one shot, at 180MB/minute with the MJPEG codec, which played fine in VLC. In both cases (VirtualDub2 and OBS), I had 1920x1080 going into the dongle, and captured (set) to 1280x720.
EDIT: Ok, I figured out why VirtualDub2 wasn't picking up the video/audio on computers #2,#3,#4. Since the first computer picked up and displayed the video as soon as I clicked Capture>Capture AVI, I thought there was something wrong when the other computers didn't pick up the video. Turns out you have to select USB Video after you click
Capture> Capture AVI. I was confused but got it figured out. As in above post #3 (Hunk91), VirtualDub2 seems to be the best choice for these $10 HDMI capture dongles. And I like VirtualDub2 because it is simple to use and it doesn't need to be installed in the computer.

[lordsmurf]

(Note that all mention below of 24 or 30 or 60 also includes more common fractional versions 24000/1001 and 30000/1001 and 60000/1001)

In US, currently:
Broadcast TV can be...For SD, interlaced or progressive 24, 30, 60 Fps.For 720, it can be progressive 24, 30, 60. For 1080, it can be 24, 30 interlaced or progressive, or can be 60 interlaced. 1080 or above cannot be 60p or above until ATSC 3.0 arrives.

Scott

... and sometimes in the same stream.

- show is TFF interlaced 30,
- commercial break progressive 24
- back to show at BFF 30

It's wild at times

[johnnyquid]

The link below has a pretty though review of these types of devices.

https://www.naut.ca/blog/2020/07/09/cheap-hdmi-capture-card-review/

[jimdagys]

https://www.naut.ca/blog/2020/07/09/cheap-hdmi-capture-card-review/

Thank you for that. Above my head but very interesting reading.

[Hunk91]

I have a similar device. One issue I found is that it only records audio in mono. For the price, I wouldn't expect much.

See here : https://forum.videohelp.com/threads/400202-Question-about-10-HDMI-Recorder#post2672935

[Hunk91]

Hi! Sorry to update this 1.5 year old posts, but I found this : https://github.com/ToadKing/mono-to-stereo/releases/tag/0.5

Apparently, all those cheap HDMI capture device presents a 96khz Mono feed that's actually 48khz Stereo but interlaced.

Source : https://github.com/ToadKing/mono-to-stereo/

mono-to-stereo

Takes a mono input and renders it as if it was an interleaved stereo input. Works on MS2109 capture devices where the audio input is a 96khz mono stream but in actuality is a 48khz stereo stream with the first left channel sample missing. In order to support this device better, accounting for this missing first sample is done by default.

Original code based off of Matthew van Eerde's loopback-capture project.