Is there any reason to downconvert 1080p to 720p for hd-dvd to avhcd?

[yoda313]

I am working on converting my hd-dvds to avchd (I only have about a dozen so it won't take forever). I already have a couple in mkv format that I will convert as is. I am pretty sure I set those to 720p when I made the mkv - it's been a long time since I did those and don't remember off hand.

I am doing one now to 720p.

My question is:

Is there any benefit to converting to 720p?

Does it take less time to convert to 720p? I am running a dual core amd x2 2.7ghz pc - its gonna take almost 9 hours to do my conversion to 720p right now - just over 7mpbs (7+gigs) for a dual laery dvdr. Would keeping it at 1080p encode faster? Would it look worse than 720p at the same bitrate?

FYI I don't have a 1080p tv but 1080i with native res of 1366x768 so I don't have to keep 1080p for max res. But if there is no strategic gain by converting to 720p in either space or quality or time should I retain 1080p?


edit fyi I'm using ripbot264 - anything faster these days or is this still the best choice? - After ripbot I'll dump the mkv into multiavchd to make a avchd. I have a seperate thread open on how to use multiavchd to take the main movie to make a avchd directly from evo - its not obvious - ripbot automatically tags the two main evos once you point it to one of the two largest files.

Also - is the bluray output option for ripbot264 really avchd? How does that output work?

[edDV]

I am working on converting a few of my remaining hd-dvd collection to avchd. I already have a couple in mkv format that I will convert as is. I am pretty sure I set those to 720p when I made the mkv - it's been a long time since I did those and don't remember off hand.

I am doing one now to 720p.

My question is:

Is there any benefit to converting to 720p?

Does it take less time to convert to 720p? I am running a dual core amd x2 2.7ghz pc - its gonna take almost 9 hours to do my conversion to 720p right now - just over 7mpbs (7+gigs) for a dual laery dvdr. Would keeping it at 1080p encode faster? Would it look worse than 720p at the same bitrate?

There should be no reason to recode an HD-DVD 1080p/23.976 file. MultiAVCHD should take it as is. The file will be large. If you are re-encoding for smaller file size, downsizing to 1280x720p/23,976 gives about a 2x advantage without increasing compression per pixel.

[edDV]

FYI I don't have a 1080p tv but 1080i with native res of 1366x768 so I don't have to keep 1080p for max res. But if there is no strategic gain by converting to 720p in either space or quality or time should I retain 1080p?

Your next HDTV will probably be 1920x1080p native. 720p conversion allows you smaller file size at similar compression to fit DVDR media.

[yoda313]

If you are re-encoding for smaller file size, downsizing to 1280x720p/23,976 gives about a 2x advantage without increasing compression per pixel.

Yes it is for smaller file size - so I can fit it on a dual layer dvdr.

So the 720p will be better at the same bitrate versus a 1080p since the smaller resolution will hold more bits? I don't know if I rephrased that properly to my understanding, is that more or less correct?

MultiAVCHD should take it as is

Well it does. My issue is how to take the two evo files to do a successful main movie merge. I have a seperate thread going on that question. That's why I fell back to ripbot since I knew it would do the merging properly - I'm sure there is a way on multiavchd but I'm not sure at the moment.

720p conversion allows you smaller file size at similar compression to fit DVDR media.

Ah that was the summation I was looking for. THanks for the advice eddv.

EDIT _ wow the 2nd pass is set for 12 hours - that puts this at a 16 hour encode.... I forgot it takes quite awhile to do this stuff......

[edDV]

1920x1080p has 2,072,600 pixels per frame

1280x720p has 921,600 pixels per frame or about 44%. So to maintain the same compression per pixel, you could reduce the re-encode bit rate to about half without significantly increasing compression artifacts. If you are recoding MPeg2 to h.264, you might be able to get down to 25-33% bit rate. Experiment on complex high motion scenes.

[jman98]

Be warned - while I think this is very uncommon, we have had reports of a few BluRay players that choke on 720p AVCHD discs. My Momitsu is one that does. It will start to play them but they almost immediately start having playback problems. It looks like what you get when frames drop. It makes them unwatchable. I would suggest that you be sure that your player is OK with 720p AVCHD before trying this.

[yoda313]

@jman98 thanks for the warning.

However I have made 720p avchds from my hauppauge hd pvr and my ps3 handles them ok.

That should be something to consider adding to the bluray player list notifications.

[johns0]

To convert the files to 720p with multiavchd click on the transcode button and select resize 1280x720 and select the bitrate you want and use 1 pass turbo for quality in the popup menu,then click apply and finishing your authoring and when it's done you will have 720p avchd folder to burn.

For 1080p files i use uncropmkv to convert to 720p and add the converted files multiavchd.

[fritzi93]

I'll add my 2 cents, from the perspective of a home video enthusiast, not a pro. My comments assume a 47" 1080p LCD HDTV, and recommended viewing distance:

Benefits of conversion to 720p?

1) As already mentioned, storage space. For an average length movie, a double-layer DVDR (BD9) is usually overkill for 720p, and BD5 is adequate, IMO. For a movie of ~ 1 hr 50-5 mins, audio re-encoded to 448 kbps, the (H264) bitrate would be ~ 4,500kbps. Consider 4,500 kbps a minimum benchmark for 1080p, below that a sharp-eyed videophile should be able to detect degradation of the picture. Divide that by 2 for 720p, as edDVD says. I didn't invent the 4,500 target, but have read it in various places. Empirically, I think it's about right with my equipment. To repeat, that's a minimum, and there will be occasional scenes where you can detect degradation even at 4,500 kbps, if you're paying close attention. More is obviously better, and above, oh, 7,000 kbps for 1080p you'd have a very hard time telling the difference (on my setup).

I usually do Blu-Ray backups to double-layer for 1080p and single-layer for 720p. For most movies, that's adequate.

2) A lot of source content doesn't justify resolution higher than 720p, including HD cable and many Blu-Rays. Again, that's on my equipment at normal viewing distance.

Faster conversion?

1) On BDRB, yes, with settings otherwise the same. On my rather slow dual-core CPU, I get ~ 13 fps on the fastest setting at 1080p, add about 3 fps for 720p.

2) Highest quality settings on most BD re-encoding software are insanely slow, a prime example of diminishing returns. The speed difference is in allocating available bitrate more efficiently, and x264 does so, but the *visible* difference between fastest and slowest is not huge. IMO, it only makes a significant difference if the available bitrate is marginal to begin with.

How about just using adequate bitrate, i.e. specify a target size adequate to the material?

Apart from DVDFab, the Blu-Ray to Blu-Ray programs available in the Tools section all rely on the same set of freeware tools.

[yoda313]

To convert the files to 720p with multiavchd click on the transcode button and select resize 1280x720 and select the bitrate you want and use 1 pass turbo for quality

How do you tell multiavchd to select the main movie? My other thread isn't getting a response so I thought I'd bring it up here.

I know the two files that have the main movie - ripbot264 gets the second one automatically.

@fritzi93 - thanks for the discussion.

I've actually gotten accustmed to 720p at 7mb on my hauppauge hd pvr.

FYI I have a 32" 1080i westinghouse. So obviously 1080p is not a necessity for my situation.

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I'm actually about to embark on an experiment. I've finished capping a hd-dvd movie to m2ts with my hauppauge hd pvr. I'm gonna make a avchd with it (capped with my xbox 360 with component cables and fiber optic for 5.1).

After that I'll pop in a mkv I made from a hd-dvd awhile back (also at 720P). I will make a avchd with the same tool - multiavchd - from the mkv. Than I'll empirically judge the two - different movies of course for now. But I can also eventually do a fresh dub to the hd pvr and compare - visually - with the mkv that was done digitally in software versus the hardware realtime cap of the same movie. Now as far as I know I don't think you can specify an odd number bitrate in hdpvr but I should be able to get close if not exact to the mkv for the pvr.

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These are big time movies I'm copying. Would it be ok to post screen shots and gspot info once I'm done with the conversions? The comparison would be interesting.....

[johns0]

To convert the files to 720p with multiavchd click on the transcode button and select resize 1280x720 and select the bitrate you want and use 1 pass turbo for quality

How do you tell multiavchd to select the main movie?

When you add the main movie into multiavchd just click on the title in the compilation window and the submenu will pop up and you will see a transcode button that you click where enter the settings that i described earlier.

You can also click on the movie clip to highlight it in the top media window and click on transcode for that selection.

[yoda313]

@johns0 - thanks.

I forgot to mention this particular title comes in two equal evo files. Could they simply be merged with the old dos command prompt copy /b prior to adding to multiavchd?

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Or could I simply add 1 and 2 consecutively in the window? But what about any potential pauses/delays in the seperation of the file?

[johns0]

You can add the 2 titles and have them play one after the other,just select play all(sequential playback) in the menu tab,no need to merge them then.Shouldn't be any delays unless the files have any overlapping playback.

[yoda313]

You can add the 2 titles and have them play one after the other,just select play all(sequential playback) in the menu tab,no need to merge them then.

Thanks. I'll have to try that next time.

[johns0]

You can add the 2 titles and have them play one after the other,just select play all(sequential playback) in the menu tab,no need to merge them then.Shouldn't be any delays unless the files have any overlapping playback.

Just remembered its the author tab in multiavchd that the play all is in,not the menu tab.

[yoda313]

@johns0 - yep saw that last night when I was going through it.

However given the length it takes to do mkv/avchd from the digital rip (on my dual core that is) I think I've decided to do the rest of my hd-dvds in realtime with my hd pvr. The results were fantastic. I dubbed it with my xbox 360 with the hd-dvd drive - through component cables and fiber optic for 5.1 audio.

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Does everyone know that the hd-pvr will capture 640kpbs dolby digital hd audio?

I don't know that the "hd" part is retained but the 640kpbs audio is transferred over fiber optic - at least according to the readings when I play it on the ps3 and use display for audio info.