Sorta Complicated Question regarding AVCHD(MTS) vs MP4 files

[Curtis Falk]

I really don’t want to clutter anything up, but I couldn’t find anything that helps me with what I want to know, which has become quite multifaceted in its own way and is quite specific. So I’ve been recording videos using a Panasonic G6 and a Zoom mic, where the audio is particularly important as they are music recordings(though this is about trying to make the most of what I have, please keep that in mind). On comparing the audio between the G6 and the Zoom, I found that I generally prefer the audio recordings coming from the on-board mic on the camera surprisingly, making the Zoom mic kinda unnecessary. So anyways, I started recording in MTS files(AVHD) and then switched to MP4 files when I read that it is better to record with MP4 if the main goal is to upload the files to Youtube. Okay. Recently I thought that I noticed that the audio quality on the old MTS files was actually better than the audio on the MP4 files(which I have been recording on for the last couple months). If this is so it will be quite disappointing. On doing a little research, I found that the audio codec for the MTS files is supposed to be quite superior to the one used for the MP4 files. Which might explain the whole thing, but the MTS files have to be converted to MP4 to be used on Youtube anyway right? However, when I convert the MTS files to MP4, I don’t notice any real difference in the audio quality.

So is there only a difference depending on which you initially record in? Like, would it be better to record in MTS files, and then convert to MP4 files, audio-wise? Or should there be no difference between an MTS file converted to an MP4 file, versus an MP4 file right off the bat? Am I just imagining the whole thing about there being a discernible difference for my purposes? Somehow I have gotten real confused, all tangled up in blue, about what is what. If someone could shed some light on this that would be truly amazing for me.

[Gary Nattrass]

This may help and AVCHD is a better codec than MP4 and in general AVCHD is a shooting format and MP4 is a more compressed delivery format. Some cameras also record PCM 16 bit 48k audio.

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.

[Don Palomaki]

As i see it the potential advantage of MP4 is it defaults to progressive which is appropriate for on-line/computer distribution, as opposed to interlaced which is generally better for TV viewing.

However, audio quality shouldn't be significantly different within the limits of home recording, unless significantly different data rates and bit depths are used, and/or really lame software is used to convert a file to a different format (e.g., from AVCHD to MP3). Compare the different file properties to evaluate and differences in audio and video specs.

If you were satisfied with the UTube quality when you uploaded AVCHD files previously I would stay with that. If I recall correctly, UTube typically does some file conversions on uploads so the file you upload is not exactly the file they end up distributing.

And feel free to keep using the Zoom - if never hurts to have a back-up audio recording.

[Pete Cofrancesco]

"...recording videos using a Panasonic G6 and a Zoom mic, where the audio is particularly important as they are music recordings(though this is about trying to make the most of what I have, please keep that in mind). On comparing the audio between the G6 and the Zoom, I found that I generally prefer the audio recordings coming from the on-board mic on the camera surprisingly, making the Zoom mic kinda unnecessary..."

There are many other factors that have greater impact to the quality of the audio than the format.

Recording the ambient from either the camera or zoom internal mic while expeditious wouldn't yield the best results and not surprising there is little difference between the camera and zoom. The advantage of the Zoom is its ability to do multi track recording.

[Don Palomaki]

Mic type and placement are significant factors in audio recording. And recording quality will be impacted by other nearby sound sources, the size of the ensemble, distance from the ensemble, reflections, room ambience, and the like.

It is worth spending some tome researching recording techniques to be able to better record the audio. The Shure web site has some whiter papers/guides on audio recording that can provide a starting point. And there is a lot more specialized material in books and more formal publications as well depending on how deep you want to go.

[Dave Fisk]

What Don says is spot on. A camera mounted mic is the last place to get good audio for this setup. Typical audio file format for production recording is Broadcast Wave files. 48Khz 24 bit.

It's all about mic placement, mic choice, gain structure, and the like.

I know that doesn't help right now with this question, but honestly, it doesn't really matter at this point. I've been down this road, and in the end it's pretty much picking an orange or an orange.

[Curtis Falk]

Thanks for the replies everyone!

Well the main question for me hinges on the differences in how the codecs work. Which I don't understand.

"the audio codec for AVCHD is Dolby® Digital AC-3, while the audio codec for MP4 is MPEG-4 AAC LC."

In the initial recording process, from mic to file saved, does the MP4 audio codec compress, or alter, the recording in a noticeable way than the same process with the AVCHD?

Like, I know they are just container files, and as such should have no noticeable difference. But does anyone know if the process that records and saves the files on the Panasonic G6, the process itself, alters the audio in a noticeable way? Via compression maybe? Or something else?

Thank you for your patience! I'm sorry if this is annoying

[Gary Nattrass]

Both audio codecs involve compression and if the camera also records in AVCHD it may be doing a muxed 5.1 and that may affect the stereo imaging and account for the difference in quality.

Check on your edit software too as I know that from my canon HF11 there are options in FCP to ingest in dolby or in true stereo via AVCHD.

It is normally a good process to import AVCHD in another format for editing as it can be very processor and memory heavy, I personally ingest AVCHD from my canon HF11 in pro res LT and make sure it is set to true stereo and not 5.1.