VHS Decoding and DVD ripping . . .
Steve Davies
1.) I have quite a lot of VHS tapes I want to digitise and have made a start using the Elgato Video Capture stick, (Image attached.) and while this connects nicely between my Mac and the Video recorder, and is quite easy to use, I am a little disappointed in the size of the file it outputs, its rather small.
I am not sure if this is typical of digitised VHS data, perhaps I am expecting too much, I just wondered if anyone else has used this method and can comment on their findings.
Equally, I would be interested to hear of any other recommended options there are for this process?
2.) I have several DVD box sets that I have purchased over the years, and I would also like to digitise these, (Preferably at full resolution.) can anyone recommend my best option for achieving this?
Thanks,
Steve.
Sam - MacAmbulance
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Jason Davies
On 4 Dec 2024, at 19:26, Sam - MacAmbulance wrote:
DVD is only marginally better, it’s digital already so you can only rip at full quality. MakeMKV is good for ripping direct from a DVD, then Handbrake for converting to MP4.
echoing this, and noting the weirdness about MakeMKV making you download regularly but apparently no way I can find to buy a licence.
If you feel lazy, I've also used Macdvdripper in the past, for a one-stop bit of software (but not free). It lets you poke around and be sure you're selecting the right file, as DVDs tend to be full of weird configurations once you look at the way they've put it together behind the menus.
It also offers to upscale to HD using AI, so that'll be fun as people grow extra fingers etc. (tbf it might do a pretty good job, depending on what it's working with).
Cheers,
Jason
Stephen Watson
On 4 Dec 2024, at 21:31, 'Jason Davies' via Sussex Mac User Group <sm...@googlegroups.com> wrote:
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Steve Davies
Steve Davies
Sam - MacAmbulance
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MacAmbulance Ltd.Providing Affordable Mac/PC Support and Web Development |
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Steve Davies
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Regards
MacAmbulance Ltd.Providing Affordable Mac/PC Support and Web Development |
MacAmbulance Ltd. is a registered company in England & Wales, registration number 8466597 |
On 5 Dec 2024, at 18:42, 'Steve Davies' via Sussex Mac User Group <sm...@googlegroups.com> wrote:
Jason Davies
> * Interestingly, the converted mp4 file game in at a huge 23 gb, I think I need to play with the Handbrake settings to get this down to a similar size to the original file.
I did loads of encoding on my 2010 mac pro thinking it was fast back in the day. I did a test run with my M1 Mac mini 2020 and it was about four times faster lol.
Cheers,
Jason
Steve Davies
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Sam - MacAmbulance
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MacAmbulance Ltd. is a registered company in England & Wales, registration number 8466597 |
<Handbrake settings.jpeg><MKV2MP4 app.jpeg>
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Steve Davies
Sam - MacAmbulance
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MacAmbulance Ltd.Providing Affordable Mac/PC Support and Web Development |
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Steve Davies
Cliff Wootton
Paul R Owen
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Paul R Owen
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Cliff Wootton
There are some fine points to add in order to get the best results. I'll try and keep this simple but it is a very complex topic at the level you need to operate at to get the best results and there are several important pitfalls to avoid.
If the source video is from a UK VHS tape, the visible picture size after ingest is more likely 768 pixels across x 576 lines high at 25 frames per second. That picture aspect ratio is 4:3 unless the image is stretched to fit 16:9 widescreen (1024 x 576). Wide screen is still digitised at 768 pixels wide. That (anamorphic) stretching is labelled as the pixel aspect ratio on some encoding tools.
The picture is split into two separate scans with odd and even lines. We call this interlacing. These 'half' frames exist at distinctly different times on a 50 fields per second timebase. Any movement in the view will have changed from field to field. Moving objects exhibit a horrible combing effect if you just slam them into a progressive single field format. They need to be de-interlaced carefully with smart motion compensation applied.
Sam was absolutely right about VHS having very low horizontal resolution. It is limited by the highest recordable frequency and is theoretically 333 pixels across at best. Oddly we can tolerate lower resolution in the horizontal axis. This is why VHS looks so soft compared with DVDs. You should also make sure the heads are clean and the VHS player's tracking is correct because that can cause issues with syncing and source picture quality.
The framing is 625 lines for the full picture but you lose some lines for ancillary data services (teletext/copy protection) and flyback. So, stretching the image to 720 lines in the vertical axis is scaling the visible 576 lines up by 1.25. Because that's a non-integer ratio, some lines will get interpolated. Scaling up won't improve your picture quality but it will result in a bigger output file and it will look very nasty if you don't de-interlace it first. TVs have pretty good scaling software so this is best done at playback.
The p in 720p means progressive single field vertical scanning and VHS is ALWAYS interlaced, two fields. So are DVDs. If you see a combing artefact on fast moving objects when you pause the video, it hasn't been properly de-interlaced.
DVDs have a native resolution of 720 x 576 interlaced SD (Standard Definition) encoded with MPEG-2. That's 720 pixels wide not 720 lines high. They cannot carry 720p video. By convention, we specify horizontal resolution first.
Encoding tools describe the same video format in different ways. H.264 is also called MPEG-4-Part 10 or Advanced Video Coding (AVC). Ignore MPEG-4-Part 2. It was an earlier codec that wasn't popular and not as good.
H.265 is also known as HEVC and MPEG-H-Part 2. It should deliver files that are 50% smaller than AVC and works up to much higher resolutions so it's good for 2K (Bluray), 4K and 8K.
Transcoding upwards from MPEG-2 into H.264 should be OK if you choose a high enough output bit rate. Transcoding is not the same as completely decompressing and recompressing, which might introduce undesirable artefacts and blockiness. Transcoding does not fully decode the video but just rearranges the blocks in the new output format. This is possible because the codecs are essentially working the same way.
You will get better quality if you invoke a de-interlace filter and keep the image size to what's on the tape or DVD. A small amount of sharpening might help visually but the codec won't work as efficiently and you will get bigger files.
Also bear in mind that only the black and white image is handled at full resolution. The colour is reduced to half the resolution because our eyes can tolerate it. This is a legacy from the way Analog video was transmitted and digital encoders have inherited the same idea to make the files smaller.
There is a really good (free) tool called ffmpeg but you need to use that from the terminal command line. There are graphical UI wrappers for that which make it easier to use but the command line gives you more control. It may even be buried inside your preferred tools.
If you tweak the output size to be the same as the source video and do some pre-processing before compression and code with HEVC it might look quite good and come out at a smaller size.
Jason Davies
This is really helpful, thanks Cliff. I've never quite got to grips with de-interlacing (and will have to read this again);)
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Cheers,
Jason
Steve Davies
Sam - MacAmbulance
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MacAmbulance Ltd. is a registered company in England & Wales, registration number 8466597 |
Martin
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