Mixing AVCHD bitrates

[curlyween]

I'm contemplating the jump from SD miniDV to AVCHD, and looking at the Panasonic HDC-SD60 (looks to be very good bang-for-buck), or possibly the Canon HF M300 (but it's $250 more). My sister has a Canon Legria HF10 (I think) and we're planning on a holiday to China and we'll probably take both cameras.
My question: The Canon has a maximum bitrate of 24Mbps, the Panasonic 17Mbps. Can two different AVCHD bitrates be used in one editing project (Premiere Pro CS4)? Will this have performance/encoding implications, or should we be better off, say, lowering the Canon to 17Mbps as well?

[poisondeathray]

No additional problems mixing footage of the same type (AVCHD) with different bitrates. But it's hard to edit AVCHD natively (sluggish) with CS4. You need a fast system , or use a digital intermediate like cineform . CS5 is many times smoother if you have a cuda enabled graphics card.

Potential problems do occur however, when you have different specifications like frame rate, dimensions (e.g. a pal camcorder vs. ntsc camcorder)

[edDV]

Consider Cineform Neoscene digital intermediate as a mixed format solution.

Normally 17 Mb/s mode records 1440x1080i. 1920x1080i at 17 Mb/s will have excessive compression artifacts.

24 Mb/s mode is usually 1920x1080i. Some camcorders may allow both 1440x1080i and 24Mb/s.

[curlyween]

Thanks poisondeathray,

I do understand the impact editing AVCHD has on a PC system. That's just another thing I have to bear in mind with my proposed move to HD.
How good is Cineform? Does the re-wrappering to avi have any impact on end-quality? Does the addition (edits) of titles, transistions etc. done in (say) CS4 impact on the end AVCHD product? Obviously I'm a HD noob, but I don't want to jump in blind.

edDV - Thanks for your reply. Correct me if I'm wrong, but all the specs I've seen has the Panasonic HDC-SD60 @ full HD (1920x1080) @ 17Mbps. If it isn't then I will probably go for the Canon (or would this be the better choice anyway?).

[edDV]

edDV - Thanks for your reply. Correct me if I'm wrong, but all the specs I've seen has the Panasonic HDC-SD60 @ full HD (1920x1080) @ 17Mbps. If it isn't then I will probably go for the Canon (or would this be the better choice anyway?).

It looks like the HDC-SD60 lacks a 24Mb/s recording mode. There are 50% more pixels at 1920x1080i vs. 1440x1080i. This calls for 50% more bit rate. If you record 1920x1080i at 17 Mb/s, expect more compression artifacts in the original file.
http://panasonic.net/avc/camcorder/hd/hs60_tm60_sd60/specifications.html

[poisondeathray]

How good is Cineform? Does the re-wrappering to avi have any impact on end-quality? Does the addition (edits) of titles, transistions etc. done in (say) CS4 impact on the end AVCHD product? Obviously I'm a HD noob, but I don't want to jump in blind.

quality wise, the neoscene variant is fairly good. It's visually lossless - so you won't be able to tell the difference, unless you look at single frames and zoom right in. It's not free, and you need lots of free HDD space (filesize will increase about 5-10x), download the free trial and have a go

it's not only re-wrapping, it's re-encoding to cineform. re-wrapping would be a lossless transformation (and still difficult to edit)

titles/transitions do not impact the end product when using CS4 natively, because everything is re-encoded anyways when using native AVCHD

[curlyween]

There are 50% more pixels at 1920x1080i vs. 1440x1080i. This calls for 50% more bit rate. If you record 1920x1080i at 17 Mb/s, expect more compression artifacts in the original file.

edDv, now you've got me concerned. I know quality is in the eye of the beholder, but should I be concerned about the difference between 24Mbps and 17Mbps? For holiday/family videos is there an issue? I'd hate to spend over $700 on the Panasonic then think bah, I should've spent the extra $300 for the Canon . From what I've read/been told, the Panasonic has better image stabilisation, but the Canon has a better lens (just a couple of the differences, I know).
What I'm thinking is: the only way is make a decision is to test each camera out - record to an SD card on each one and see how it looks at home.

[poisondeathray]

Yes the only way to know for sure is to shoot them side by side and examine them

Other factors contribute to the overall quality: the lens, sensor, optic, signal processing - all that comes before the compression. There might be large differences between models

You cannot judge by the bitrate alone. There are different implementations of AVCHD compression. The compression differs drastically between AVCHD implementations. AVCHD by some panansonic models usually offers better compression (this means better quality at a given bitrate) than canon's. They have higher number of reference frame and use better quality encoding. But other panasonic models are pure garbage - e.g. the native GH1 uses "AVCHD", but the implementation is horrendous. Even at 17Mb/s it looks worse than other cameras at 9Mb/s. It doesn't use b-frames, uses baseline profile, 1 reference frame and the low quality shows.

[edDV]

There are 50% more pixels at 1920x1080i vs. 1440x1080i. This calls for 50% more bit rate. If you record 1920x1080i at 17 Mb/s, expect more compression artifacts in the original file.

edDv, now you've got me concerned. I know quality is in the eye of the beholder, but should I be concerned about the difference between 24Mbps and 17Mbps? For holiday/family videos is there an issue? I'd hate to spend over $700 on the Panasonic then think bah, I should've spent the extra $300 for the Canon . From what I've read/been told, the Panasonic has better image stabilisation, but the Canon has a better lens (just a couple of the differences, I know).
What I'm thinking is: the only way is make a decision is to test each camera out - record to an SD card on each one and see how it looks at home.

True you can't judge on any one spec. The lens, sensor, processing electronics, recording format and recording bit rate all matter.

But other things being equal, bit rate is very important for picture quality especially if the recorded video will be edited and re-encoded. It often comes down to resolution vs. bit rate for picture quality factored by the codec used. In the pro world, bit rate gets priority over resolution because it is assumed the video will be edited.

Consumer AVCHD is normally recorded 17 Mb/s for 1440x1080i and 24 Mb/s for 1920x1080i. I haven't heard of any breakthroughs in camcorder hardware encoding that allows 17 Mb/s 1920x1080i compression while maintaining 24 mb/s quality.

[2Bdecided]

Check camcorderinfo.com if they've reviewed these models.

Try to find raw footage to download and compare.


The jump from SD to any half-decent HD camcorder (i.e. not the cheap junk that claims HD but has a $0.50 lens!) is going to please you quality-wise. You probably do want the best you can afford, but remember that any re-encoding you do, and the settings on your TV, are going to do as much to reveal/hide artefacts as the camcorder itself.

More important than any of this is what's behind the camera (i.e. you!).

You can always wait for the technology to mature further, but you may regret all the stuff you recorded to DV when you could have been shooting HD. I know I do.

Cheers,
David.

[pepegot1]

Think before you jump into a can of worms! Unless you have great equipment and software, knowlege would also help, you are looking for hours of pain. This technology has a ways to go before it even approaches the facility of SD. But, if you must, just remember the above when problems come. Try Canon HV40. You can record in SD and HD. I remained with SD because HD is still in a primative stage and I don't have hours to spend on things that take minutes in SD mode, or the horsepower for HD. Besides, more often than not you will be forced to change to DVD, if you wish to distribute to others.

[filmboss80]

Think before you jump imto a can of worms! Unless you have great equipment and software, knowlege would also help, you are looking for hours of pain. This technology has a ways to go before it even approaches the facility of SD. But, if you must, just remember the above when problems come. Try Canon HV40. You can record in SD and HD. I stay with SD because HD is still in a primative stage and I don't have hours to spend on things that take minutes in SD mode, or the horsepower for HD. Besides, more often than not you will be forced to change to DVD if you wish to distribute.

Agree 100%. If you really want HD with far fewer headaches, don't ignore the oft-overlooked HDV format.

[edDV]

My normal workflow is HDV camera (Sony Z1U or Canon HV) through Vegas Pro to HDV+Blu-Ray+DVDR. Results are preditable and good. When I need to integrate AVCHD source or do heavy effects, I use the Cineform Neoscene digital intermediate. So far this works for me.

If/when I can upgrade the workflow, I'm tending to XDCAM-EX over AVCHD. Main issue holding me back is flash memory cost and performance. Tape is cheap and works better.


PS: So far the clients see no benefit to flash RAM for them and see no reason to cover the extra media costs so it would come out of my pocket. From my point of view, flash RAM adds nothing to my productivity, just the opposite.

[curlyween]

Many thanks to everyone for your replies.
I have spent many hours at camcorderinfo.com, and that's probably the problem - too much information can be a bad thing....

I have considered the HV40 but it's $500 more than the Panasonic, and one of my rationales behind upgrading was to get away from tape. I don't have anything against tape per se, but the thought of having a nice, small flash memory camera appealed to me. The HV40 is bigger and heavier than the HDC-SD60 and the HF M300 (in fact it's bigger than my current SD camera - an old Canon MVX330i) and I don't want a bigger camera.

Another thing that has intrigued me - and please set me straight: HDV maxes out at 1440x1080 (@ 25Mbps I believe), yet the sensor in the HV40 is 1920x1080. So what happens to those extra 480 pixels? How does that affect the end picture quality, or is there some other magic going on? I have been somewhat confused about that for a while.
I understand that HDV is a lot easier to edit, but if I was to export HDV to AVCHD (I have a Blu-ray player) how does that 1440 resolution translate to 1920?
Sorry to bombard you with so many questions, but the more I read and research, the harder the decision becomes .

[poisondeathray]

Another thing that has intrigued me - and please set me straight: HDV maxes out at 1440x1080 (@ 25Mbps I believe), yet the sensor in the HV40 is 1920x1080. So what happens to those extra 480 pixels? How does that affect the end picture quality, or is there some other magic going on? I have been somewhat confused about that for a while.
I understand that HDV is a lot easier to edit, but if I was to export HDV to AVCHD (I have a Blu-ray player) how does that 1440 resolution translate to 1920?

"non square pixels"

the pixel aspect ratio is 1.3333 (or 4/3)

so 1440 is stretched to 1920 width on playback. Of course 1920x1080 would be better, but only if the compression was good enough (adequate bitrate, better compression standards). MPEG2 @ 25Mb/s is not adequate for quality for a 1920x1080 frame size from a 1pass hardware encoder

it's compatible with blu-ray or avchd discs, right out of the camera. HDV is MPEG2 (50i for PAL regions)

[edDV]

Another thing that has intrigued me - and please set me straight: HDV maxes out at 1440x1080 (@ 25Mbps I believe), yet the sensor in the HV40 is 1920x1080. So what happens to those extra 480 pixels? How does that affect the end picture quality, or is there some other magic going on? I have been somewhat confused about that for a while.
I understand that HDV is a lot easier to edit, but if I was to export HDV to AVCHD (I have a Blu-ray player) how does that 1440 resolution translate to 1920?
Sorry to bombard you with so many questions, but the more I read and research, the harder the decision becomes .

Allow me a quick history of 1440x1080i. Other input welcome.

First, 1440x1080 is 4:3 aspect using square pixel. Not that 4:3 has ever been supported for high def, but from a processing point of view, square pixels are most compatible for cross platform filters.

Second, interlace video is not friendly to vertical resize. We can dig deeper into that statement but even standard def interlace is fixed to 480 lines per frame, 240 lines per field (576/288 for PAL).

Third, horizontal resize is easy within an interlace structure. Pixels can be non-square in the horizontal direction. Usually a flag code is included to indicate final display aspect ratio. This is done for standard definition where 720x480 or 704x480 are used for both 4:3 and 16:9 aspect ratio (720x576 or 704x576 for PAL).

Forth, bit rate compression results in visible artifacts regardless of codec. Assuming a clean source, the onset of visible artifacts at a given bit rate is usually a function of the number of pixels per frame. Or looking at it from a different perspective, you can reduce compression artifacts at a given bit rate by reducing the pixel count.

Consumers and advanced hobbyists can think of bit rate as a free variable but in the pro telecommunications world, digital bit rates tend to be limited to those of existing technologies (e.g. ATM, Ethernet, satellite transponders, recording tape, etc).

In the broadcast studio context, digital video was first implemented as uncompressed standard definition SDI (SMPTE 259M) at 270Mb/s for 10 bit 4:2:2 video + 8x 20 bit PCM audio channels. TV stations, TV networks and post production facilities were built with extensive SDI networks in the 1990's.
http://en.wikipedia.org/wiki/Serial_digital_interface

When HDTV was introduced, it was decided that it must fit into the existing 270 Mb/s SDI infrastructure. Subtracting the PCM audio and other metadata 144 Mb/s was left for HD Video. Uncompressed 1920x1080i video+audio required a 1,485 Mb/s data path (SMPTE 292M).

So, given this 144 Mb/s limitation, an optimal HD standard had to be created. Keep in mind that multiple recodes were typical in the broadcast chain as the video was edited and distributed. For this reason, the video needed to be frame based (no temporal compression) with minimal recode loss.

First to go was 10 bit gray scale. 8 bits would have to do.

Next to go was 4:2:2 sampling. 3:1:1 sampling was selected.

Next to go was resolution. Tests showed users preferred the second and third generation picture quality of 1440x1080i vs. 1920x1080i at the required compression. This reduced the number of pixels per frame by one third.

After all that, 1440x1080i HDCAM intraframe DCT compression worked out to about 3x, about the same as 10bit, 4:2:2 704x480 90 Mb/s DigiBeta. Most HDTV network broadcasts are derived from HDCAM tape masters.
http://en.wikipedia.org/wiki/HDCAM

Tomorrow, I'll try to extend this to HDV and AVCHD formats.

[2Bdecided]

There are 50% more pixels at 1920x1080i vs. 1440x1080i. This calls for 50% more bit rate.

33% more, surely? 50% more would be 2160, not 1920. Your point still stands though!

Anyway, what do you think of 1920x1080p50 at 28Mbps H.264? That's what Panasonic is selling now (e.g. the panasonic hdc-sd700).

Pure pixel numbers suggests the bitrate should double from 1080i50 to 1080p50, but of course it doesn't work like that: H.264 works far better without interlacing, and it's nice to have native progressive video to avoid the (progressive) display from having to deinterlace. So, win-win situation.

I haven't got one, but initial reports seem to suggest that this 28Mbps 1920x108p50 is now the best quality at the price - which implies 28Mbps H.264 is a good choice (though I've seen samples at slightly lower bitrates that also look fine).

Cheers,
David.

[2Bdecided]

Think before you jump into a can of worms! Unless you have great equipment and software, knowlege would also help, you are looking for hours of pain. This technology has a ways to go before it even approaches the facility of SD. But, if you must, just remember the above when problems come.

12 years ago, it was easier to use VHS than DV. I'm glad I jumped to DV back then though.

Try Canon HV40. You can record in SD and HD. I remained with SD because HD is still in a primative stage and I don't have hours to spend on things that take minutes in SD mode, or the horsepower for HD. Besides, more often than not you will be forced to change to DVD, if you wish to distribute to others.

I'm amazed you're having trouble with HDV. A vaguely modern PC, and a capable NLE (e.g. Vegas HD - it's less than £30) and you should be fine. It's at least as easy as DV was five or more years ago. Easier probably - Vegas doesn't crash as much now, and there's even more help on the net these days than back then.

When DV was new, you needed a very good new PC to use it (and/or a proxy format).
When HDV was new, you needed a very good new PC to use it (and/or an intermediate format).
When AVCHD was new, you needed a very good new PC to use it (and/or an intermediate format).
Now 1080p50/60 is new, you need a very good new PC to use it (and/or an intermediate format).

When anything is new, you can end up being one of the first people to figure it all out. You'll need a new PC to do it properly - factor this in!

If you want your videos to have any longevity, then shooting SD in 2010 is a very strange choice.

Cheers,
David.