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Official GX1 hack development topic
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  • Nice. I just upgraded to GX1. Hehe.

  • Thanks guys.

    GX1 is complicated. Due to MP4 and some changed code.

  • Is there any MP4 advantage over AVCHD other than some tablets can edit MP4 files?

  • mp4 wrapper is conversely more supported on pcs, devices etc... than avchd. Pany sells it as 'instantly stick your vids up on the web...!'

  • What about the image quality?

  • Current info about the GX1 mp4 mode;-

    Bitrate readings - Stock Settings PAL 25p MP4

    • bit_rate_value_minus1 = 23436 (they say approx 20M)
    • cpb_size_value_minus1 = 16405 (16M buffer)

    Other info:

    • num_ref_frames = 2
    • GOP 12/15 for 1080 25p/30p (i and p frames only allowed - conformance to baseline 66 std)
    • Seemingly different frame limits for each of the 25p/30p mp4 modes from VKs ptools pic - nice! AVC profile = 66 (Baseline) - info about this profile -

    MPEG-4, Advanced Video Coding, Baseline Profile Description:

    Baseline is the least complex of the three original MPEG-4_AVC profiles (Baseline, Main, and Extended), i.e., it places the least demand on a decoder. The Baseline Profile is constrained in several ways, including a limit to intra (I) and predicted (P) slice types (slice is the MPEG-4_AVC term for a single macroblock or a set of macroblocks that make up a portion of an individual picture.) For a discussion of additional contraints and the levels that may be used in this profile, see Appendix A in Part 10 of the standard, pp. 204-211.

    The Part 10 Standard:

    * Sensor:

    MP4: NTSC

    • [Full HD] 1920 x 1080, 30fps (sensor output is 30p) (Approx.20Mbps).

    • [HD] 1280 x 720, 30fps (sensor output is 30p) (Approx.10Mbps)

    MP4: PAL

    • [Full HD] 1920 x 1080, 25fps (sensor output is 25p) (Approx.20Mbps)

    • [HD] 1280 x 720, 25fps (sensor output is 25p) (Approx.10Mbps)


    • [Full HD] 1920×1080, 60i (sensor output is 30p) (FSH:17Mbps) / [HD] 1280 x 720, 60p (sensor output is 30p)(SH:17Mbps)


    • [Full HD] 1920×1080, 50i (sensor output is 25p) (FSH:17Mbps) / [HD] 1280 x 720, 50p (sensor output is 25p)(SH:17Mbps)
    gx1_mp4_mode_1080p25_progressive_12 GOP.png
    1412 x 902 - 639K
    GX1 720p25HD mode.png
    1550 x 717 - 956K
    GX1 Stock 720p25HD on a death chart - buffer analysis.png
    720 x 787 - 37K
  • Bitrate readings - Stock Settings PAL 25p MP4

    Yep, if you look, they are higher than 1080p24 settings (with formally higher bitrate) :-)

    Even more difference is in 720p MP4, as they are higher than settings for 16Mbit modes :-)

    I absolutely do not get why this 10Mbit is used.

  • Hmmm... Judging by the charts above they set up rate control with a target of around 10Mbit.

  • @driftwood

    Yep, bitrate is set at 10Mbit, but bit_rate_value_minus1 and cpb_size_value_minus1 do not match. Same for 1080 MP4 modes (as they are more approariate for 22-23Mbit.).

  • Thats true.

  • Thank you for the excellent results of your hard work Vitaliy!

  • Yes, thank you Vitaliy for your great efforts. Can't wait to unleash the GX1.

  • Thank you Vitaliy and your team for your awesome, awesome work. Next paycheck I'll make sure to send more money your way.

    A question for you hackers: from what you have written, it seems like the sensor can output both 25fps and 30fps depending on NTCS/PAL settings. Does this mean that the sensor's framerate can be set via firmware? What about 60p? Is that actually possible?

    In anycase, looking forward to your hack.

    Thank you again, J.

  • Hi, with your hack, is there any chance of changing the auto bracketing to a wider stop range?. Currently you can do 3 frames at a max of 1stop under and 1stop over. I would like to do a 3 frame exposure bracket at -2stops, normal, +2stops... Thanks

  • I know this is nothing easy or even possible to do. But I would love a feature for makro focus stacking. Press the shutter button once, and the camera moves the focus point from near to far in X steps and takes X pictures in between.

  • Greetings Vitaliy from Jakarta, Indonesia! A few days ago I donated Option 5 thinking that a GX-1 hack was possibly a long way but when I didn't get an answer to my email, I came back to your website and found "Official GX1 hack development topic" which is great news. My question, is it possible to make HDMI to TV show the footage while recording video, instead of just playback? I ask because in addition to you making the recording options all manual I would like to use a HDMI monitor to focus while shooting and I can not use a monitor because you can only use an external monitor for playback.

    Again, great work you are doing!!

    Jakartaguy (in Jakarta, Indonesia)

  • My question, is it possible to make HDMI to TV show the footage while recording video, instead of just playback?

    Get GH2. This is hardware thing.

    Next time use

  • Sorry for improper post. My key comment was to thank-you for the exciting work you are doing for GX-1 camera owners!! If you ever come to Jakarta I will buy you a beer :-)


  • If you ever come to Jakarta I will buy you a beer :-)

    Thanks. I'll count on it. Big box of beer :-)

  • I am on finishing stages for both cameras. Alpha version will be ready pretty soon.

    Sorry for delay, guys.

  • Don't worry Vitaliy, it's great news either... Cameras are pretty awsome with original fw too, so it's not big deal if you finish hack later... Especialy when you were sick. As was said before, health is more important. Just curious, if the alpha will be available to all or only for alpha-testers only? Will be glad to try it on my G3 ASAP, 'cause theese news are getting me more and more excited :) Once again, thank you very much for your hard work.. Box of beer is ready for you when you come to Slovakia some day ;)

  • Alpha is available to alpha team :-) As it can contain some nasty bugs.

  • Fantastic news, G3 can't wait for the beta !

  • Cool stuff. Thanks Vitaliy.