AVCHD vs. MP4 ?

My Panasonic G6 camera has the choice between recording video in AVCHD and MP4. What are the pros and cons between the two ?
As far as I know myself there should be no difference in picture quality, but AVCHD using Dolby and MP4 PCM for sound encoding, but I might be wrong.

On my Canon camcorder I record in AVCHD, which I convert in FCPX to "optimized " mov-files before editing.
Does MP4-files recorded on the G6 also benefit from being optimized before editing in FCPX?

AVCHD is a far superior codec than plain MPEG-4. AVCHD is based on MP4, but is a much cleaner, much more advanced. Personally, I stay away from generic MP4 whenever possible. H.264, AVCHD, and others based off of the MP4 specs are all way far and beyond the original, outdated, great-grandfather.

It is all Long-GOP, which will benefit from Optimizing, yes.

Thanks, - guess I will stick to AVCHD.

Ah, - I just found the article I was referring to in my first post. What I didn´t notice when first reading it was the different scan modes used by the two codexes - highlighted in the quote below).

To my knowledge interlaced is aimed at broadcast (scans every second line in the picture) while progressive scans the whole picture and is giving a more filmic look.

Can anybody elaborate on this?

Here is the quote from community.sony.com

The primary difference between the AVCHD format and the MP4 format is the file structure (aka container format) used to save the video codec and audio codec. Although both formats record the video codec as MPEG-4 AVC/H.264, the AVCHD-formatted video is saved using a .M2TS file extension and the MP4-formatted video uses a .MP4 file extension. In addition, the audio codec for AVCHD is Dolby® Digital AC-3, while the audio codec for MP4 is MPEG-4 AAC LC.
IMPORTANT: AVCHD is suitable for creating AVCHD or Blu-ray Disc® (BD) recordings and watching on an HDTV. Whereas, MP4 can be saved as a single movie file and is much easier to move, copy, and upload to websites.
Specifications for both formats are provided in the tables below.
AVCHD format:
Video codec MPEG-4 AVC/H.264
Audio codec Dolby Digital AC-3
Picture size/Scan mode (Aspect ratio) 1920x1080/60i, 50i (16:9)
1440x1080/60i, 50i (16:9)
Audio channels/Sampled frequency 2 channels/48 kHz
5.1 channels/48 kHz
Container format MPEG-2 System (.M2TS file extension)
Compatibility Compatible with the Blu-ray Disc® format
Compatible with several recording media devices, such as Hard Disk or Memory Stick® media
Compatible with xv.Color technology
MP4 format:
Video codec MPEG-4 AVC/H.264
Audio codec MPEG-4 AAC LC
Picture size/Scan mode (Aspect ratio) 1440x1080/30p (16:9)
1280x720/30p (16:9)
640x480/30p (4:3)
Audio channels/Sampled frequency 2 channels/48 kHz.
Container format MPEG-4 System (.MP4 file extension)
Compatibility Compatible with the Apple® QuickTime® format
Compatible with various recording media and networks, including PlayStation® Network video
NOTES:
AVCHD is an acronym for Advanced Video Codec High Definition.
AVC is an acronym for Advanced Video Coding,
AAC is an acronym for Advanced Audio Coding.
LC is an acronym for Low Complexity.

I see the thank you button below, but wanted to give an extra thanks for your information that you provided on AVCHD and MP4. Just what I was looking for.

If that document is from a Sony site then it's not necessarily relevant to the implementations in your (Panasonic) G6. Here's what I understand:

AVCHD is a very specific H.264 implementation with industry-agreed format and bitrate. Sony, Panasonic, and a few others use it (I think the Canon C100 shoots AVCHD?). The AVCHD standards allow for 1080p24/25/30 and 1080i50/60, as well as 720p24/25/30/50/60. Maximum bitrate is usually quoted as 24Mbps, but you'll sometimes see 28Mbps.

The limitations of AVCHD are that the strict spec doesn't allow for 1080p50/60, and the bitrate is arguably rather low.

Panasonic's DSLRs have long been technically capable of producing higher-bitrate recordings (hence the popularity of hacking the GH1 and GH2 cameras); with the G6 and GH3 they made those higher bitrates available without hacks. Since the AVCHD spec doesn't allow for higher bitrates, the files are instead wrapped as .mp4. It's important to note that these are still H.264-compressed files: MPEG4 is a file format which allows for several different codecs. The confusion is that the older MPEG codec shares a similar name, but most MPEG4 files today will be using the H.264 codec. Certainly, Panasonic's DSLRs do.

...then it gets more confusing because H.264 is sometimes called 'AVC.' Yeah, the industry really messed this up for us all. You'll sometimes see "MPEG4/AVC" - which means H.264 video in a .mp4 file.

...then there's the .mov/.mp4 thing, which really does my head in. The MPEG4 file format was based on Quicktime, so there's often not much difference. Indeed, on a Mac most apps will open such files whether you call them .mov or .mp4.

...and if you're still not confused, hold tight: Panasonic's implementation of H.264 allows for high-bitrate long-GOP compression, or very high-bitrate intraframe-only compression (ie. each frame treated separately). Everyone expected the latter to be higher quality, but in practice it usually isn't - the interframe compression in H.264 is very smart, and why even lowly AVCHD looks as good as it does.

In theory the iframe-only stuff is easier to edit, but in practice I find FCPX plays happily with any of these formats. I only transcode for multicam projects.

One caveat: I actually don't know what formats the G6 supports. The GH3 does all of the above, but I'm not 100% sure which bits the G6 handles. Most of it, I think?

Excellent. Just one addendum. AVCHD now supports 1080p50 and 60.

I will say excellent too.
The G6 supports both AVCHD and MP4 in all the formats you mention and yes, - AVCHD in the G6 now also supports 1080p50 and 60.

I had two main reasons for starting this thread.

1: The AVCHD file structure (.MTS) is pretty complicated, - if no difference in quality between AVCHD and MP4 I will prefer MP4.

2: I read on EOSHD.com that AVCHD is a pretty "fragile" codex that does not take much tweaking/grading in post before it breaks up. Then I wondered if MP4 might be a more robust codex in post. But as AVCHD and MP4 by the end of the day are pretty close related - at least as I understand - this might not be the case.

Anybody who can enlighten us on this?

Both loose generational quality fast. You don't want to re-encode them. Thus, the beauty of ProRes.

bluefonia wrote: I will say excellent too.
The G6 supports both AVCHD and MP4 in all the formats you mention and yes, - AVCHD in the G6 now also supports 1080p50 and 60.

I had two main reasons for starting this thread.

1: The AVCHD file structure (.MTS) is pretty complicated, - if no difference in quality between AVCHD and MP4 I will prefer MP4.

2: I read on EOSHD.com that AVCHD is a pretty "fragile" codex that does not take much tweaking/grading in post before it breaks up. Then I wondered if MP4 might be a more robust codex in post. But as AVCHD and MP4 by the end of the day are pretty close related - at least as I understand - this might not be the case.

Anybody who can enlighten us on this?

If you plan to import your footage using FCP X, the fact AVCHD file structure is "more complicated" is moot.
FCP X imports these just fine, provides for the creation of "Camera Archives" (exact duplicates stored on your drives, for backup and retrieval), and allows you to make selections on input (like importing just 20 seconds off a 1-hour recording). No such features are available, AFAIK, for the mp4 version.

Ah yes, I forgot about AVCHD 2.0 and its 50/60p modes. The bitrates are arguably rather low, but it's nice to have on occasion.

EOSHD.com can be a good read, but I hope it's fair to say that the author's knowledge is not encyclopaedic. When he's good he's very good, but when he's spouting nonsense it can be hard to tell. As with all sources – including anything you might read in a forum dedicated to a weird NLE which "isn't used by professionals" (ahem) – read widely and form your own opinions!

My take on AVCHD is that it was a much better compromise than was generally recognised when it came out. Four or five years ago forums seemed full of people rubbishing it for its low bitrate, but failing to recognise the difference in compression efficiency between AVC/H.264 and, say, MPEG2.

However, AVCHD is limited as a result of being an 8-bit 4:2:0 codec. If you really push it in grading you will see colour banding and blocking. But it's not inherently worse than other 8-bit 4:2:0 codecs: the limitation is a result of the sampling, not the codec itself. Higher bitrates help stop the picture turning to mud when you whip-pan across foliage, but good AVCHD implementations are surprisingly robust. It's the colour sampling which hurts, particularly if you're trying to shoot fairly flat and apply a 'look' in post-production.

There's a decent case to be made that the days of 8-bit codecs are over: now that camera sensors can comfortably resolve 11 or so stops range it's crazy to throw away so much of that data just because the codec can't keep up. Hence the rush for 10-bit ProRes or raw recording.

This is one of the reasons the Panasonic GH4 is so interesting. Internally, it'll record 4K video in H.264 at 100 Mbit/sec – given there are roughly 4x as many pixels that's a similar sort of bitrate to AVCHD, and it's still 8-bit. For many situations that'll be 'good enough,' just as AVCHD is today. HDMI output, meanwhile, can be 10-bit, which makes for a very interesting 1080p workflow with an external recorder. And if you really want to turn the thing into a mini-Alexa you buy the fugly add-on box, pipe 4xHD-SDI to a 4K recorder, and spend my typical production budget on SSD cartridges.

Oh, and BenB's right about generation losses in H.264. If you need to work on a shot outside FCPX, export it to ProRes and keep that clip in ProRes for the rest of post. There's no harm in editing with H.264 masters, but anything that gets rendered should move to - and stay in - ProRes.

jjsanderson@
Thank you, that was very good explanation, just what I needed.

Before the G6 I only had a Canon Legria HF S100 ( PAL version of Vixia). All the stuff recorded on that camera was in AVCHD and I have had no issues when grading the footage in FCP. I just got curious when I read the article on EOSHD.com about AVCHD vs. MP4 as the G6 can record in both.
As far as EOSHD.com I think you are quite right, which is why I put up the topic here too to get a second opinion.

Yes, the GH4 is very interesting. Just a petty they have not adopted the brilliant built-in stabilizer that Olympus
apparently has in their cameras. Guess I will wait for the GH5

Yes, Olympus' IBIS sensor stabilisation is amazing, I'd love to see that on the Panasonic cameras. Unlikely to happen, though, I'd have thought. What remain to be seen is whether Olympus get more serious about video.

Incidentally (and back on topic, hurray!), the new InertiaCam smoothing in FCPX is sometimes fabulous. It's saved a couple of shots in one of my recent films which suffered from having been handheld on the GH3 with a 35mm Nikkor.

lichinho wrote: ...
If you plan to import your footage using FCP X, the fact AVCHD file structure is "more complicated" is moot....FCP X imports these just fine, provides for the creation of "Camera Archives" (exact duplicates stored on your drives, for backup and retrieval), and allows you to make selections on input (like importing just 20 seconds off a 1-hour recording). No such features are available, AFAIK, for the mp4 version.

The problem I've encountered is the limited native Mac OS X support for AVCHD -- you can't see thumbnails in Finder, can't see the AVCHD clips as discrete files, can't use Preview to browse through them, etc. Quicktime will open them but it's very clunky and slow.

If you are importing all the AVCHD material into FCP X, it's no problem. However if you have a large amount you want to sift through before import, it's difficult without using ClipWrap or similar. Even that is slow for large amounts of material. VLC can read it but has artifacts.

We use the Canon XA25 and HF-G30 which can record either AVCHD at 28 megabit/sec or MP4 at 35 megabit/sec. We usually use MP4 for the above reasons. I haven't tried the import on a range from AVCHD, maybe I should revisit that.

What's wrong with importing with FCP? You can selectively import multiple ranges from each clip. I don't think there is a quicker more flexible importing tool.

Tom Wolsky wrote: What's wrong with importing with FCP? You can selectively import multiple ranges from each clip. I don't think there is a quicker more flexible importing tool.

Ah ha, - I was not aware of that. Thanks, will try to figure that out on next import

Tom Wolsky wrote: What's wrong with importing with FCP? You can selectively import multiple ranges from each clip. I don't think there is a quicker more flexible importing tool.

Productions with a high shooting ratio ( en.wikipedia.org/wiki/Shooting_ratio ) would have to either (a) browse and selectively import vast media content using *only* FCP X, or (b) import everything, select and consolidate. If you can only do selective import with AVCHD, then that creates two discrete ingest workflows. The non-AVCHD material must be somehow culled before import, or else you import it all.

We are actually trying to figure out the best path forward, so would appreciate any further advice or discussion.

What do you mean by non-AVCHD media? All camera media behaves this way when accessed from a camera archive. Always. The only difference is when camera material has been brought from the recording media onto the hard drive without the camera structure that FCP can identify. This is a mistake, but it can be worked around. The media can be put into a disk image, which FCP will read and behave as camera media.

In this age of vast hard drive space at cheap prices most producers, except those working with GoPro cameras that shoot miles of redundant media, usually ingest everything and keep everything. It's cheaper to keep than to have to go through later and see if you missed something.

Tom Wolsky wrote: What do you mean by non-AVCHD media? All camera media behaves this way when accessed from a camera archive.

I was referring to the previous post saying range selections on import only worked for AVCHD, not MP4: www.fcp.co/forum/4-final-cut-pro-x-fcpx/...5-avchd-vs-mp4#41167

If that is wrong and it works for all media types, that's great and I'll explore that.

Tom Wolsky wrote: ...In this age of vast hard drive space at cheap prices most producers, except those working with GoPro cameras that shoot miles of redundant media, usually ingest everything and keep everything. It's cheaper to keep than to have to go through later and see if you missed something.

We sometimes have several GoPros, several DSLRS and three camcorders running hours each day. We could easily do 300GB in a weekend. That is highly compressed camera media which becomes much larger if optimized. If several concurrent projects are in post-production, all that must stay on line, so you could potentially fill up a Pegasus R6 pretty quickly.

When we used Premiere, it wasn't as much an issue since we worked only with camera media files.

Do you suggest importing using optimized media for cases like this, or not creating optimized media until the rough cut is made and consolidated, or what?

This is a great discussion and I appreciate your advice.

I don't know what hardware you're using, but nothing in the last few years needs to optimize AVCHD.