AVCHD vs mp4

CalebKCalebK Website User Posts: 435
i just realized my camera can record as an AVCHD or Mp4.  I find AVCHD annoying because it gets read slowly and i have to export each individual clip out of it.  It turns out to take me along time per film I'm doing to do that.
can i turn it to mp4? Are their some disadvantages?

Comments

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,244 Ambassador
    You can turn to mp4,but, AVCHD is h.264 (mp4) compression in a different container.

    Since both formats are h.264 compression, chances are you won't see much change in performance.

    It get a bit more complicated: AVCHD tends to use a higher "Profile" type and CABAC encoding--CABAC is a "lossless" scheme, which means a CABAC encoded stream will have higher image quality than a non-CABAC encoded stream.

    So, the question is, what "profile" and entropy coding does your camera use for it's mp4 recording?

    Best suggestion I can make, since I don't know what difference, if any, your camera uses in profile and entropy settings, is to try shooting something AVCHD, reshooting MP4, and seeing if there's a difference in performance.

    Either way, it's probably still better to transcode whatever you shoot to DNxHD before editing.
  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,244 Ambassador
    http://www.avsforum.com/t/1467038/mp4-versus-avchd-and-bitrates
    This is a pretty good article discussing AVCHD vs mp4 in a bit more detail, in case I didn't explain things well.
  • MatthiasClaflinMatthiasClaflin Website User Posts: 674 Just Starting Out
    edited May 2014
    I have always wondered why everyone likes to edit in DNxHD. I know I would totally use it if my computer could handle it but any kind of playback is incredibly choppy since I have a sub-par computer. I have always shot and edited AVCHD, and although I'd love to move away from it, I have yet to justify it. When you record something in AVCHD, does changing the container actually help at all? Your computer can't "make up" for data/details that are lost when it was recorded to AVCHD, so why would you want to transcode?
    @Caleb, what kind of camera are you using? If I'm not mistaken, canon cameras 35mps MP4 is the same as the 24mbps AVCHD as far as quality goes, the AVCHD is just a smaller file.
  • __simon____simon__ Website User Posts: 113 Just Starting Out
    @Matthias, you're correct transcoding to DNxHD can't add back what was lost, the reason for doing it is that DNxHD is a lot easier for the computer to decompress than H.264. Having said that, I'm not convinced it's true, sure using software decoding DNxHD uses less CPU but my graphics card seems to be able to playback 1080/50p using about 3% of it's GPU and 2% of the CPU, that's far less than decoding DNxHD is software ...
    In regard to AVCHD vs MP4, in particular CABAC being lossless and thus having a high quality, it's not the fact that CABAC is lossless but that it compresses more efficiently than the alternative. So say for example a 24mbps AVCHD will have better quality than a 24mbps MP4 since more data has to be thrown away at an eariler stage to get the same file size but as Matthias points out a 35mbps MP4 can have the same quality as the 24mbps AVCHD.
Sign In or Register to comment.