I applaud the fact that Panasonic made the 720p23.976 recording native in many of their AVCCAM cameras. (AVCCAM is Panasonic’s brand for AVCHD professional.) However, I am concerned about the fact that they did this in a very incomplete way. In this article, I’ll cover the advantages of native progressive recording, how Panasonic and other brands have done a complete job in other cameras, and why there are missing certain native progressive recording modes in current AVCCAM models.
Advantages of native progressive recording
Although with tape recording (where native progressive recording was complex and rare), with tapeless recording it is much more common, and less complex. What gets the most press about native recording is the so-called “24p” mode, which in video is almost always really 23.976p, although some camera manufacturers and NLEs go half way to express it as “23.98”. The reason that “24p” native recording gets more press is because “24p” -when recorded as a pulldown over “60i/p” (almost always really 59.94i/p)- is the mode that has caused the most noticeable trouble in the past, since it has caused the most difficulty to get camera footage onto a true 23.976p timeline, as I explained way back with my When 25p beats 24p article. With native 23.976p recording on tapeless formats, many -although not all- of the “24p gotchas” have been alleviated.
But there are other advantages of native progressive recording, even when we’re talking about a low-to-medium framerate that doesn’t use a complex pulldown. If you haven’t guessed yet, I’m talking about 25p and 29.97p. With any of the framerates mentioned so far -23.976p, 25p, and 29.97p-, there’s a bandwidth benefit by using native recording, since it avoids bandwidth waste by avoiding the recording of “garbage frames”. Depending upon the method used, native recording can either allow half of the compression, or allow for double the recording duration. Either way, native progressive recording is good, and fortunately, both Panasonic and Sony have offered it with other cameras.
Use of beyond 23.976p native progressive recording by Panasonic
- The AG-HPX170 offers native progressive recording of 29.97p (sometimes called 720/30pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HVX171 offers native progressive recording of 25p (called 720/25pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HVX171 also offers native progressive recording of 29.97p (sometimes called 720/30pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HVX200A offers native progressive recording of 29.97p (sometimes called 720/30pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HVX201A offers native progressive recording of 25p (called 720/25pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HVX201A also offers native progressive recording of 29.97p (sometimes called 720/30pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HPX300 offers native progressive recording of 29.97p (sometimes called 720/29.97pN by Panasonic) in order to achieve double duration on a P2 card.
- The AG-HPX301 offers native progressive recording of 25p (called 720/25pN by Panasonic) in order to achieve double duration on a P2 card.
- The AG-HPX301 also offers native progressive recording of 29.97p (sometimes called 720/29.97pN by Panasonic) in order to achieve double duration on a P2 card.
- The AG-HPX370 offers native progressive recording of 25p (called 720/25pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HPX370 offers native progressive recording of 29.97p (sometimes called 720/29.97pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HPX500 offers native progressive recording of 29.97p (sometimes called 720/30pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
- The AG-HPX500 offers native progressive recording of 25p (called 720/25pN by Panasonic) in order to achieve double duration on a P2 card, using the DV100 códec (aka “DVCPRO HD”).
In all of the above mentioned situations with DV100, the native progressive recording is optional. These cameras also offer non-native recording, presumably to offer direct file compatibility with the old DVCPRO HD tape format. In the case of recording using the new AVC-Intra códecs on those cameras that offer it, native progressive recording is the only way to record, since it makes more sense, and (to my knowledge) there is no tape format using AVC-Intra.
Use of beyond 23.976p native progressive recording by Sony
According to Juan Martínez of Sony, the PMW-EX1, PMW-EX1R, PMW-EX3 and the HXR-NX5 cameras exclusively offer native progressive (internal) recordings in all progressive framerates. In the case of Sony’s implementation of native progressive recording on the mentioned cameras, the advantage is not double capacity/duration, but to offer lower compression. However, presently in 720p modes the HXR-NX5 only offers 720p50 and/or 720p59.94, depending upon whether it is the 50Hz version, ±60Hz version, or whether it has been upgraded to WorldCam status. I hope that Sony will add the other framerates to the 720p mode in the future, and that they do so natively.
STOP THE (VIRTUAL) PRESS: JVC reinforces my point
Dave Walton, Asst. Vice President, Marketing Communications for JVC USA Professional, just confirmed my suspicion that JVC Professional also handles this issue the logical way:
Allan,
Our ProHD solid state memory cameras (GY-HM100, GY-HM700, GY-HM790) record progressive signals in accordance with the file formats and specifications established by Sony for their XDCAM EX product line (.mp4 files) and by Apple for their Final Cut Pro line (.mov). As with Sony, in all cases we record the progressive signals in the format selected by the user without remapping them to another higher frame rate. The advantage is that at any given bit rate, the amount of compression will be less with lower frame rate signals. […] Frankly, it surprises us that anyone would use (frame duplication) when recording MPEG (any flavor) to solid state memory.
Potential bandwidth footprint of AVCCAM/AVCHD per frame versus what’s currently being done
Since the lowest-compression/highest-quality AVCHD available today is the so-called 24Mb/s (24 megabits per second), of which 21Mb (21 megabits) is for the video, I have based my calculations on the theoretical maximum of 21 available Mb/s, and all of the numbers refer to the video only.
The highest framerate currently available with these cameras is 59.94p. By dividing 21Mb by 59.94, we get a ±0.35Mb footprint per frame. The lowest framerate currently available is 23.976p. Because the current Panasonic AVCCAM cameras (thankfully) do offer native 23.976p recordings, if we divide 21Mb/s by 23.976p, we get a much more generous ±0.87Mb footprint per frame, which means much lower compression. Because the Panasonic AVCCAM cameras don’t currently offer native 720p25 or native 720p29.97 recordings, we are being swindled from a bandwidth perspective! When recording 720p29.97 with repeated frames over 59.94p (as with an AG-HMC150, AG-HMC151, AG-HMC40, and even apparently with the upcoming AG-HMC80 & HMC81), each frame only gets ±0.35Mb a footprint (as do 59.94p frames) when they could have gotten a ±0.70Mb footprint if Panasonic offered native recording of 720p29.97. By the same calculation, each 25p frame (on capable models) should get a ±0.84Mb footprint, but only gets a ±0.42Mb footprint due to repeating frames over 50p.
What has happened with the native progressive recording in Panasonic’s AVCCAM so far?
At NAB 2010, I had to go to the Panasonic booth four times before I was able to find Jan Crittenden -the current AVCCAM product manager- to ask about this issue. I’m not going to publish the lame excuses I got from other Panasonic personnel before finally reaching Jan. Her response was that she agreed with me, and that she had only recently inherited this particular product line. She said that apparently either the prior product manager didn’t request native recording in the missing modes, or didn’t fight enough to make it happen. I expressed my thanks for being so honest about the situation. When I asked her about the possibility of this issue being fixed on current AVCCAM models via firmware, she responded that she doubted it, because this is so deep in the circuitry of the current cameras. Fortunately, she said that it will be done in future cameras.
What should we do about it?
As I wrote in my preview article on the upcoming AG-HMC80 & AG-HMC81, the current AVCCAM cameras don’t presently have any direct competition in their price rage with 720p recording anyway, so it’s not like you can consider another brand, because currently, no other manufacturer is doing any better in this price range and camera type.
The nature of spatial resolution versus high temporal resolution (framerate) naturally involves tradeoffs. That’s why some networks choose to broadcast 720p, and some choose 1080i. The tradeoff is fair when choosing among the 23.976p and 50p/59.94p options in the current AVCCAM cameras, but it isn’t fair when choosing 720p25 or 720p29.97. If we choose a mid framerate -like 29.97p- with the current AVCCAM cameras, we are not getting any bandwidth bargain. So what we need to understand is that if we do it, it is for an esthetic reason, and/or because we know that an important part of the final delivery must be done on 720p29.97p, i.e. the iPad (for compatibility reasons).
Why the iPad will dictate your shooting framerate & shutter speed
See the related article: Why the iPad will dictate your shooting framerate & shutter speed.
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None of the manufacturers listed in this article is paying Allan T©pper or TecnoTur LLC specifically to write this article. Some of the manufacturers listed above have contracted T©pper and/or TecnoTur LLC to carry out consulting and/or translations/localizations/transcreations. At the date of the publication of this article, none of the manufacturers listed above are sponsors of the TecnoTur programs, although they are welcome to do so, and some are already sponsors of ProVideo Coalition magazine.