Quality Loss recoding AVC files to HEVC

glenpinn

Member
Hi everyone, i was over in the VideoHelp forum recently to see if anyone was able to definitively say for sure that recoding 720p and 1080p AVC (mp4) files to the new HEVC codec would drop the video quality to a point where you can visually see any difference between the original AVC file and the new HEVC output file if watching them on the same screen or TV.

Obviously one will need to calculate the right bitrate for the HEVC conversion that would offer the same or a similar output quality as the source file.

In the VideoHelp forum there seems to be a lot of ill informed nut heads who seemingly are fixated on this notion that you should never reconvert any video files from one format to another because your going to see a drop in quality between the original AVC file and the new HEVC file when played on the same computer screen or TV, and i don't believe this to be the case at all, based on my conversions done using VRD Pro.

I know VRD has smart rendering where by it calculates the so called required HEVC bitrate to convert an AVC file, and it seems to be about 35% lower than the bitrate of the AVC source file from all the reconversions that i have done so far.

I have played many of my 720p and 1080p AVC source files on my 65" 4k smart TV and then played the new HEVC conversions, and i cannot see any visible drop in video quality on any of these files, not with my eyes at least, and neither can my wife and daughter as well.

Can someone please explain how all this works, because i understand that one should retain the original source file to retain the greatest possible quality, but now that we have HEVC that seems to allow us to have our files in the same quality as the AVC files but at a much smaller file size, so what real reason would there be for not reconverting the AVC files, as long as we use the right video bitrate for the HEVC conversions.

Also, i am noting that the MKV container seems to be more widely used than the traditional MP4 container, and i am curious as to what the real benefits are between using either of them.

Cheers
 

jmc

Active member
I believe you are correct...with high bitrate files.
I mean there must be a loss technically but (most) human eyes are not going to see it.

I fussed on a thread here that as a test I converted dvd.mpgs to X264s and HEVCs and found that to my eyes the X264 was better quality EVEN at the same bitrate and Dan203 mentioned the below... -------------(I convert at 1.3Mbps. So no HEVC for me)

---------------------------Quote--------------
" Dan203
Senior Developer
Staff member

Mar 15, 2021
Most of HEVCs improvements are designed for 4K/HDR and have little effect on lower resolutions. If you're encoding HD then HEVC might actually look a little worse."
-----------------------------------------------------

jmc
 
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jmc

Active member
Also, i am noting that the MKV container seems to be more widely used than the traditional MP4 container, and i am curious as to what the real benefits are between using either of them.
I believe I've read of more problems with dvd players and TVs playing MKVs then playing MP4s.
Searching through my VRD problem file I found...

1. " We only support 3 kinds of subtitles... NTSC closed captions, PAL teletext and DVB subtitles. And we only support them for passthrough, which means you can only keep them if the output contianer also supports them. MKV does not support any of them, so all subtitles are lost when saving to MKV. MP4 supports closed captions, but not the other two. The only format that supports all 3 is TS."

2. "One more thing... MKV is not the best container to use for editing in VRD. Most MKV files store their time stamps in milliseconds. That's fine for playback, but it's not high enough resolution for frame accurate navigation. In VRD we use 90Hz ticks so when we open an MKV we have to convert. Because the resolution of the MKV time stamps is too low the conversion isn't perfect and it can cause some issues. If at all possible you should use TS or MP4 instead of MKV. Or if you have to use MKV set the time stamp resolution higher so that we can more accurately convert and avoid the issues. (MKVToolnix can do this)"

jmc
 

glenpinn

Member
MKV files have always played perfectly for me over the years, back in the early days of HD video you needed an external media player (such as the Western Digital Live TV Player) plugged into the TV and you connected your USB stick or hard drive to that to play those types of files as most TV's did not support many formats.

Later on TV's had built in USB ports but were still limited to just a few supported format, but when HD became the norm most TV's would support direct playing of MP4 and MKV, plus others.

Our 65" LG 4k smart TV plays everything, and it upscales lower resolution video very well, and i have been amazed at the quality of some of the low bitrate 720p videos that i often play, downloaded Documentaries for example, or Youtube videos.

It was after i started watching 720p and 1080p videos and saw just how nice they looke on that 4k TV that made me think more about recoding all my AVC files to HEVC at an equal quality bitrate (as calculated by VRD in their presets) and then i realized that there would be no way that any human eye could see any quality loss anyway, even if it was 10%, but i am sure that by using the built in AVC to HEVC conversion bitrate within VRD, any loss of quality would be very minimal, and not really affect the output quality in the way that some idiots in the VideoHelp forum are suggesting.

I also believe that one is going to get much better results from re-encoding high resolution videos that were recorded at higher bitrates than converting lower resolution files with low bitrates.

A lot of my downloaded Documentaries are 720p AVC (MKV or MP4) with an average bitrate of around 1.5 kb/s so these will have already lost a lot of original quality while dropping the files to a suitable format for downloading or streaming, but they still look nice upscaled on my 65" TV, and when i converted some to HEVC the bitrates were around 1.0 kb/s and i see no visual quality loss myself.

In the end, many will say not to bother converting already converted video files (like mine) to HEVC because it just creates another encode and therefor another drop in quality, and that the only time you should convert AVC files to HEVC is if you have the original AVC source file (from a camera etc) and you want to drop the file to HEVC at an equal quality to save on storage space, or if you are wanting to drop the output resolution, then saving it to HEVC is definitely the way to go.
 
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glenpinn

Member
This link will show you exactly what i mean about forums and some of the absolute crap that many posters come up with, you even have 2 members in there, both posting ill informed and completely wrong facts, and then argue with each other about who is right or wrong, both are wrong, but nobody has bothered to tell them, so other dimwitted readers then need to decide who's information they should believe.


In the VideoHelp forum, there are a small group of members who very clearly know their stuff, but they treat other members with complete contempt and disrespect in the way that they reply to members who are very clearly new at video conversions, and treat them like they are dummies, and i don't like this, and if you challenge these idiot in any way, they get shirty and start calling you names.

I got banned from that forum a few years ago because i often made references to VRD Pro, and some of these regular members (the bobby know all's) would report me believing that i was promoting VRD and getting paid for it, which was absolute crap, i referenced VRD a lot simply because i know that of all the basic editing/encoding software out there, it is the best all rounder, able to do things that most others were not able to do, and even better than Handbrake or VidCoder, both of which i was forced to use a few times while waiting for VRD to add new features that those 2 tools already had in place.

The issue i have with Handbrake, unlike VRD is with selecting output bitrates, in VRD the Devs have selected default bitrates for each given profile or task that you might use, i don't know how they set these default bitrates, but i trust them to be right, with Handbrake or Vidcoder you must manually select Constant Quality and the RF setting Quality Setting using a slider, or you select an Average Bitrate, and if you don't understand bitrates then you would have no idea what your output file quality will be like.

Anyway, apologies for ranting on, it just makes me angry when i try to find answers to stuff and have to read so much rubbish in forums like the one i posted in the link above.
 
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