Screenshot Quality

2006 DVD

2010 DVD

The most difficult pictures to take with the camera have always been screenshots. Screen images are a very important part of BeebMaster and I am very rarely happy with the images produced by the camera. The results are variable in the extreme and some of the pictures I have had to settle for have been downright poor.

I had tried ways of recording the output from the BBC micro, originally onto video recorder, to capture images to use as screenshots. I never got this to work. Using the UHF output on the Beeb produced a very unsatisfactory picture, the composite video output was black-and-white only, and using an RGB-to-SCART lead would not work either. For technical reasons which were beyond me, a video recorder or DVD recorder didn't seem to be able to pick up the RGB signal produced by the BBC when it's fed in via SCART.

In November 2006, I started using a DVD recorder to capture screenshots from BBC micros using the Composite Video output. Although by default it is monochrome, it is very easy to add colour to the Comp Video signal, which has allowed me to produce high quality screenshots using this method.

There's much more on how to turn the monochrome Composite Video into full colour here.

The general procedure was to connect up the Beeb in question to the DVD recorder video the Composite Video. I use the recorder's High Quality Setting, which can fit about an hour of recording on a DVD. I initially used two re-writable DVDs alternately for doing the recordings, although this has now expanded to four. These are erased and re-used once I have finished with them, although I keep the captured video files.

For each picture I want to capture, I usually record for about three seconds, pause, set up the next picture, and record again. For "live action" activity, such as a utility or game running, I would normally run the sequence two or three times and record it each time to get the best chance of capturing everything I need.

Once the recording is done, I copy raw video files from the DVD onto my PC and then wipe the DVD for re-use.

Before using Ubuntu, I used to have to trawl my way through the video, pressing pause every time I wanted a screenshot, using the save screenshot function, typing in a file name, checking the saved file was the frame I wanted and not the one before or the one after, and then carrying on to the next picture.

Linux has a very handy function called "ffmpeg" which can be used from the command terminal. It is for converting video files between different formats, but also allows a video file to be converted to jpg, in other words, extracting the frames from the video. It will extract every single frame, which becomes rather unwieldy, but also allows extraction of frames at a specific time interval, so I use it to create frames at intervals of 1.5 seconds, which is ample for what I need.

The end result is a set of images which I can then look through and choose the ones I want to use on my website. From this point on, the method is the same as for making the picture sets from digital camera photographs. The frames are extracted at a size of 768x572 for the 2006 DVD recorder, so I leave them at this size. There is no need to crop or rescale them, so I use Phatch to suffix them and take the quality to 70%, and then to make the preview size images.

Sometimes it isn't convenient to connect the DVD recorder to the actual machine I want to capture, for reasons of space. To see what's going on, I have to have a monitor connected to the DVD recorder and there isn't always room to put the recorder and monitor right as close to the machine being captured as the lengths of cable and availability of sockets will allow.

It can also be a bit of a fiddly job to try to fit the little colour composite capacitor to a machine that doesn't have it already, especially if it's one of my machines in a permanent installation and not just a demonstration setup.

Luckily, that's where my Econet comes in, because I can use the *VIEW command to view the station I need to capture on a machine located some distance away with the colour modification applied and enough space to connect everything together and record the VIEWed screen.

Using this method in 2009, I was able to obtain masses of screenshots from my Master Compacts, in colour, even though the Compact doesn't support the colour addition to its composite video signal. I even wrote my own version of *VIEW, which updated in real-time. This was quite a programming achievement for me, because it had to take into account hardware scrolling, mode changes, and logical colour palette definitions!

In December 2009, I was able to record my Acorn Atoms using a composite video lead which came with the first of my Atoms. Unfortunately, the picture was extremely unstable on the DVD recorder, constantly rolling vertically around the screen. I had first tried this in September 2009 but had given up after being unable to stabilise the picture. I tried again in December 2009, thinking I might be able to record sufficient material to extract frames at the moment the picture lined up into the correct position. The result was a little bit hit-and-miss but generally it worked. To prevent myself going dizzy whilst doing all this, I also had the Atom connected up to a TV set via the RF output so I could at least see what I was doing!

In summer 2010, I replaced my cheapo DVD recorder with a much better JVC one. The new one understands RGB, which means I can now record onto DVD using a BBC RGB-to-SCART lead. This has allowed me to make even better quality Beeb screenshots than I could achieve with the composite video output. It has also meant for the first time I could record the screen output of some of my later 32-bit Acorns which don't have a composite socket, such as my A5000 and A7000.

The biggest benefit of all has been that I can now record proper screenshots of the Domesday System, which was not possible previously as the BBC micro RGB overlay always got lost in the recording.

The method of making the DVD recording into a picture set is much the same as with my first DVD recorder, but the frame size on the JVC one is 720x576. Also the ffmpeg command has been superseded by avconv which requires very slightly different parameters but is basically the same. Since January 2016, I've not reduced the JPEG quality when suffixing the images in Phatch. File size isn't so much of a priority now, and producing screen images with minimal JPEG compression artefacts is more important, although it will be a few years before these new, higher quality images filter through!

FFmpeg seems to have made a reappearance in Ubuntu, so I'm now back to that, and I'm using Converseen instead of Phatch with effect from Ubuntu 18.04.

Unfortunately, the JVC DVD recorder has been on the blink over the last couple of years. It seems to eat DVDs now, occasionally breaking down in the middle of a recording, rendering the disc unreadable and losing everything recorded so far.

In February 2011, I was given the suggestion that I might be able to record a more stable Atom picture using a PC TV tuner card. In fact, my PC has a TV card because I made it part of the specification when the machine was built for me in August 2003. I think I had the idea at the time that I might be able to use it to view pages from Teletext at a time before I had much experience of using Acorn Teletext Adapters.

The Tuner card has a composite input, so I could use the Atom composite video socket. It took a bit of doing and I had to use an unusual video setting - PAL 60 - to get the picture, but once this was tweaked, I could use VLC to display a live Atom picture and take screenshots whenever required.

You can see more about my two DVD recorders by clicking on the picture links above.

In around October 2017 I discovered the RISC-OS application !Snapper which saves screenshots either as an Acorn sprite file, or PNG or JPEG. I sent some suggestions to the developer, Chris Johnson, who incorporated a number of changes to this very useful tool, which I now use to make screenshots on my RISC PC 700. Possibly I have a unique version of !Snapper, I'm not sure! It means I can now get screen images at the exact screen resolution without the distortion the DVD recorder was producing.

In January 2020, I took delivery of a Raspberry Pi RGB-to-HDMI converter which has been developed with the BBC Micro in mind. It allows the RGB output to be fed into an HDMI (or VGA) monitor, and also has the facility to do screen captures. After quite a bit of experimentation during 2020, from September onwards I have been making screenshots using the RGBtoHDMI unit, and the JVC DVD recorder has finally been decommissioned. The picture quality is very good, and I can get larger pictures than the 720x576 size from the DVD recorder.

The downside is that it's necessary to power off the Beeb and take the SD card out of the RGBtoHDMI to look at the pictures, so in February 2021 I bought some HDMI USB capture sticks which work on my Ubuntu PC with OBS Studio. With a second RGBtoHDMI from December 2021 permanently connected to Station 201, using an HDMI splitter, I can see the picture on the monitor as well as having it fed into the USB capture stick and I now use this method for screenshots. In July 2022, I added a dictation machine foot pedal to my PC and programmed it to shortcuts for OBS Studio so that I can use my feet to take the screen picture any time. Station 201 is of course on my Econet, as are most of my other machines, so I can use an Econet remote screen viewer utility to grab another station's screen at Station 201. If I then move the foot pedal to underneath the machine in use, with the viewer running on Station 201, I don't even have to be anywhere near my PC or Station 201 to take a screenshot of any Beeb on my Econet.

For occasions when it's still necessary to capture the screen from the actual machine, I still use a DVD recorder, and my latest model from September 2021 is a Sony RDR-HXD770 which has replaced the JVC one. This has a hard drive, but to get pictures onto my website, I still need to dub the hard disc recording to DVD then process the frames in my PC, which is a bit cumbersome. However, the Sony DVD recorder has an HDMI output which I can feed into the USB capture stick and do screen captures with OBS Studio like a do with my RGBtoHDMI. At first, the results were not good as the Teletext picture came out all jagged, but some adjustments to the picture settings in the DVD recorder have improved that to an acceptable level. It's still not as good as RGBtoHDMI, but very handy for situations where I need to capture the full SCART output of a Beeb or later Acorn, such as the Domesday Machine where the video comes from the SCART output of the LV-ROM player.

My newest bit of screen capture equipment, and the most expensive, to date is the Open Source Scan Converter, or OSSC. I actually bought this in April 2022 to do Archimedes screen captures as I thought it would be better than the DVD recorder. The OSSC is quirky and I find it difficult to tune in to individual machines, so it gets very little use. I think it's more for gaming consoles than Acorns. Certainly it's hopeless with Teletext as it can't display mode 7 properly at all, which is a bit of a disappointment, even though Teletext screen capture wasn't envisaged for my use of the the OSSC anyway.

Updated 1st May 2023