Bitrate of XAVC 1080p60 Mode?

[Jack Zhang]

Just curious about what the F5 and F55's XAVC 1080p60 bitrate is compared to what Panasonic is announcing. (Basically 1080p60 in AVC-I 100mbps)

Easiest way may be to get content browser screenshots or a Mediainfo report.

I'm curious because if the F5 and F55 have more bitrate in that mode, IMHO, it wins the 1080p60 battle.

[Cees van Kempen]

1080p60 is 200 Mbps
2K at 60p is 200Mbps
4K at 60p is 600Mbps

[Jack Zhang]

So that does mean XAVC out of the box will be supporting the mode that AVC-Ultra Class200 at 1080p60 will require a upgrade for on current hardware. I call that putting XAVC ahead of AVC-Ultra.

[Alister Chapman]

XAVC also uses a method of including SPS (sequence parameter set) and PPS (Picture Parameter Set) into the video data stream. This means that rather then just using a generic profile for the way the video should be encoded and decoded the cameras hardware encoder can tailor the encoded data distribution depending on the images being recorded and then include information within the video stream that will then tell the decoder how best to deco the material. Video goes into the dedicated encoder chip and is analysed before encoding to figure out how adjust the encoder settings to get the best results. The video is then encoded with the modified encoding parameters while those parameters are included within the clips data stream. The decoding hardware or software can then look at this data to make sure the video is correctly decompressed for the best possible results. This makes the codec more efficient and minimises artefacts. The vast majority of codecs use a fixed generic encoding/decoding profile.

There's more info on XAVC here: XAVC Specification Overview | XAVC | Sony

[David Heath]

Originally Posted by Jack Zhang

Just curious about what the F5 and F55's XAVC 1080p60 bitrate is compared to what Panasonic is announcing. (Basically 1080p60 in AVC-I 100mbps)

1080p/60 in AVC-Intra 100 seems extremely odd to me.

It's been long established that 60p does not need twice the bandwidth of 30p for equivalent compression quality - but that has always been assuming an inter-frame compression system. (As example, keep the I-frames the same time period apart - say 1/2 second - and double the GOP length. Since the bitrate is largely dependent on the I-frame data size, it should be obvious 60p won't need twice the bandwidth of 30p. Yet because the I frames are still the same period apart, the differences between them will be the same, hence the same compression quality for a relatively small increase in bitrate.)

But AVC-Intra is (obviously) an intra-frame system. With means that each and every frame gets allocated the same amount of data by definition. Hence for 1080p/25, each frame gets 4 Mb (0.5MB) - 100Mb every second divided amongst 25 frames. Go to 1080p/50 and that same 100Mb every second must now be distributed amongst 50 frames - so half as much data per frame, each frame now can only have 2Mb or only 0.25MB.

I'd expect to see AVC-Intra 200 used to record 50/60p. That or compromise quality. In an intra-frame system, double the frame rate and you have to double the bitrate to preserve the per frame compression quality, all else equal.

As far as XAVC goes, then yes, it and AVC-Intra are both based on H264, so have a great deal in common. But XAVC is a newer implementation, has more tricks up it's sleeve, and therefore promises higher quality for the same bitrate compared to AVC-Intra. Even so, I'd be surprised to see XAVC 100Mbs used for 1080/50p, 200Mbs (as Cees says) is far more reasonable for keeping quality up.

[Jack Zhang]

I can see nowhere in the Panasonic press release any word about Class200 in use in any of the newer 2013 launch cameras with MicroP2. Panasonic people will have to wait longer for a Class200 camera, while XAVC already has 4K 60p.

[Paulo Teixeira]

Panasonic Announces 2/3-INCH, 3-Chip AJ-PX5000G AVC-ULTRA P2 HD Shoulder-Mount with MicroP2 Card Slots, AVC-LongG at DV Info Net
"The PX5000G will offer optional AVC-Intra200 recording, which at twice the bit rate per frame of AVC-Intra100 is virtually lossless, delivering a master quality codec in an affordable, file-based shoulder-mount camera. High-resolution AVC-Proxy recording is likewise an option."

Perhaps Panasonic will show off a smaller P2 camera at NAB that uses the Micro P2 card.

[Jack Zhang]

"Optional" being the key word here. It's not included standard and has to be added to the camera.

Clarifying, I saw nowhere where Class200 comes standard with the camera.

[Ned Soltz]

I was at the press conference announcing the camera. Looking back at my notes I defintely see that the Class 200 AVC-Intra is an extra-cost unlock.

Ned Soltz

[Paulo Teixeira]

I'm not sure why it would it even matter if Panasonic released 2 different cameras with 2 different model names verses just 1 model in which you can purchase an extra feature as long as people don't have to go through many hoops to get it or if the higher bit rate option will come out much later than the release date for the camera.