USB Video Grabber Test

Test of the Logilink USB video grabber.
Technical data
Capture guide for the EasyGrabber (Part 2)

Many names

The device is sold under many names. EZ grabber, EZgrabber, EasyGrabber, STK1160, STK1150, LogiLink Videograbber USB2, ezcap168,

USB Video Grabber
The USB Video Grabber

Many buyers have trouble grabbing videos with the EasyGrabber. So did I. Since help was not available at the internet I wrote this test report. In Part 2 you get a tutorial for grabbing with the EasyGrabber.

Strengths and weaknesses

+
unbeatable cheap in price
good image quality for VHS videos, absolutely sufficient
no noise visible
adequate sound quality for normal VHS tapes and VHS copies

captures only with 25 fps or 30 fps and throws together two frames without deinterlacing.
(Subsequent deinterlacing necessary, otherwise strong comb artifacts visible in fast moving picture parts)
no video visible during fast forward of VHS tape (Preview)
below 60 Hz noise ratio reduces to 60 dB

Measured values:

Video
Image resolution
Frame rate
optical resolution via composite input
optical resolution over S-Video input

720×576
25 … 30 fps
approximately 512×384
(see example below)
Audio
Sampling rate
Resolution
Frequency response (-3dB)
Ripple (100 Hz ... 18 kHz)
Noise ratio (40 Hz ... 20 kHz)
Noise ratio (60 Hz ... 20 kHz)
Stereo Separation (1 kHz, 200 Hz high pass)

44.1 kHz / 48 kHz
16 bit
40 Hz … 20 kHz
< 0.6 dB
60 dB
> 75 dB
> 56 dB

For grabbing videos from VCR (VHS) these technical parameters are absolutely sufficient.

What can this grabber do in detail?

Image

The video grabber captures a full PAL image without border losses with 720×576 pixels.
Input signals can be composite (from VHS recorder) or S-Video. VHS video has reduced sharpness because it uses only composite signals.

The grabber adds no visible noise to the picture.

Live preview

Here are some screenshots. You can compare the capture results of the composite and S-video input with a digital DVD test image. This is not a simulation, I actually recorded these pictures with the EasyGrabber. To show you the quality of a real-world VHS tape I recorded the signal also from DVD to VHS tape and grabbed it from the recorded VHS tape.

As the screenshot of the grabbed picture were compressed to 720 pixels, I have stretched them to 768 pixels.

digital
 

Live preview of the image quality. Move the mouse over the image descriptions to see how image quality changes! Digital Originaldigital
Digital original
S-Video from DVDS-Video
S-Video, small loss of details of the fabric
Composite from DVDComposite DVD
Composite, blurred
Composite from recorded VHSComposite VHS
Composite from VHS, blurred, strong loss of details in skin and fabric, below are switching distortions of the video heads

Scaling
The Grabber captures with a resolution of 720 × 576, thus the image scales about 9% to small.
To get back correct proportions, you need to enlarge to 768 pixels in width, or you have to tell your video encoder that it must use 720 pixels that are not square (pixel aspect ratio =?? see wikipedia:Pixel aspect ratio ).

Effective visual resolution
With VHS videos already 512 × 384 pixels satisfy the required visual resolution. All details of a VCR image will be proper reproduced (I tested this via composite input that was feed from a DVD). This limit is due to the resolution of VHS, not the grabber.
Among other things, this results from the fact that the video bandwidth of 3 MHz of VHS is significantly lower than that used for analogue TV signals. An additional blurr in television arises because the lines partially overlap on screen. Therefore the real resolution never reaches the number of lines that are transferred(550 lines). This is important to know when scaling down the grabbed video.

Conclusion
The resolution of the composite input is sufficient to grab VHS videos without loss of sharpness.
A picture from DVD is sharper when recorded via the S-video input compared to the composite input.
But also S-video does not give the full sharpness of a DVD image that is transferred to TV via separate RGB signals (SCART). This is not an effect of the grabber, it results from the specifications of composite and S-Video.

VHS players do not have RGB outputs, since a composite signal is sufficient to provide the full resolution of the recorded VHS signals. SCART connectors you find at VHS players do not carry separate RGB signals.

Limits
The resolution of current analog TV broadcasts is not achieved by the USB video grabber.
Using the USB video grabber makes no sense if you want to grab high-resolution analog material.

Audio

The USB Video Grabber digitizes audio signals in stereo at 44.1 kHz and 16 bit resolution.

Grabber audio frequency response
Frequency response of the Grabber

The audio frequency response of the grabber is 40 Hz ...> 20 kHz (-3dB).
Ripple is less than <0.6 dB (100 Hz to 18 kHz).

Only with headphones you can hear a faint hum when no audio is present.
This hum can be removed with a 60 Hz high pass that is applied to the signal.

Absolutely sufficient for VHS.

Frequency Measured amplitude of the recorded signal
30 Hz -4,18
40 Hz -2,90 (this lower limit frequency at -3 dB)
50 Hz -2,00
60 Hz -1,49
80 Hz -0,89
90 Hz -0,71
100 Hz -0,58
125 Hz -0,58
160 Hz -0,19
200 Hz -0,10
400 Hz 0,02
1000 Hz 0,00
1500 Hz -0,09
3150 Hz -0,25
5000 Hz -0,26
10000 Hz -0,23
11000 Hz -0,14
12000 Hz -0,05
13000 Hz -0,09
14000 Hz -0,26
15000 Hz -0,45
16000 Hz -0,54
17000 Hz -0,51
18000 Hz -0,52
19000 Hz -0,70
20000 Hz -1,78 (this upper frequency limit of -2 dB)

Measured audio values of the EasyGrabber

Grabber noise flor
Measured noise ratio

Below 60 Hz we have interference signals, which results in an over all noise ratio of 40 dB.
This is already sufficient. An audio tape recorder also achieves only the same SNR (with inactive noise reduction).

HiFi VHS recorders reach about 70 dB Signal to Noise Ratio. Here audio is record with FM modulated HF.
The USB video grabber cannot achieve this high audio quality. If you want to get hi-fi audio from your tape your need to record audio with a seperate high-quality sound card. However this will produce delay between audio and video which you have to remove later.

You can use a simple trick to enhance the SNR of the recorded audio. As the noise rises below 60 Hz you can filter the audio track by means of any audio editor with a 60 Hz high pass filter. If your video contains mainly speech, you will hardly notice any lost of audio bandwith. By this means the noise ratio improves to very good 75 dB (Figure below).
If your video contains music, you better use a 40 Hz high pass.

I have never filtered the audio recordings made by the Logilink video grabber, as the minimum noise is hardly noticeable.

Grabber noise above 100 Hz
After filtering with a 100 Hz high pass, about 75 dB SNR

The channel separation of this grabber is as good as the noise ratio.
I have measured a channel separation of 56 dB (1 kHz test signal, recording subsequently high-pass filtered with 200 Hz ).

Behavior of the grabber when fed with distorted signals

It is interesting what happens when the grabber is fed with a distorted signal. This is more common due to disturbances in VCR tape flow and crease on VHS cassettes.
In some grabbed videos I noticed that the picture sometimes freezes shortly in motion, and then jumped to keep running. There is a plugin for Avisynth that creates a list for all frames of a film, how much they differ from the direct predecessor frame. Actually this plugin has been developed to be able to analyze films from digital copies (DVD, Blueray), whether they have been subjected to an exotic interlacing, since for the conversion between different frame rates (NTSC and PAL) often some frames are doubled. This discrupts the smooth flow of movements.
Normally you cannot apply this tool on VCR recordings. Even with still images (eg a text panel) it will distinguish much difference between two successive, seemingly identical frames because they are superimposed by noise from VHS tape. The noise is so strong that it will rise the difference index between the two identical frames above 1,000. When I attached MultiDecimate to the recorded video, I discovered a lot of absolutely identical frame copies in the image stream. These came not frome the tape. The grabber and the software has inserted them at the points, when the grapper could not catch a correct picture because of disturbances in tape flow. There are artificially generated duplicate frames.

Duplicate fill frames generated by the video grabber
Duplicate fill frames are automatically generated to replace disturbed frames

Liste mit Bildunterschieden
Differences of successive frames in the list that has been generated by MultiDecimate

Large segments of the video were completely without these duplicate frames. In other sections whole series of up to 7 consecutive frames ware filled with identical digital duplicates.
In the graphic below I have summed up the total of duplicate fill frames over the duration of the video. It is apparent that the number of faults is greater in some sections.

Grabber noise above 100 Hz
Total amount of filling frames in a grabbed VCR recording

Duplicate frames are not an error or disadvantage of the USB video grabber. Something must be done if the input signal is disturbed. A repeat of the last undisturbed image is acceptable.
It would be a question of enhanced post-processing, to identify those duplicates in the film and replace them later by intermediate images that are automatically calculated from the last valid and next valid frame. This task is not trivial, since up to 7 frames must be replaced by a image sequence. For suggestions, I am grateful.

How to grab video from VCR

At Amazon, there are many disappointed buyers of this unbeatable cheap video digitizer.

My first results also were disappoiting. My videos had dropped frames and strong interlacing artifacts.

The trick is just take care of some things and use the right software. Then you can achieve very good results with this device. The following page helps you successfully digitizing your videos.

> Grabbing VHS video with the USB Video Grabber

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