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audio extraction: do .mp4 videos always contain .m4a audio?



 
 
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  #1  
Old October 17th 18, 02:30 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
J. P. Gilliver (John)[_4_]
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Posts: 2,679
Default audio extraction: do .mp4 videos always contain .m4a audio?

I sometimes want to extract just the audio from a video clip (e. g. so I
can play it on my SatNav/GPS [I have an old one that doubles as an audio
player; I gather modern ones don't do that!], or just because the video
is static or irrelevant).

I would very much prefer to extract the _original_ audio stream:
although _I_ am unlikely to hear the difference, the purist in me feels
that any transcoding _in theory_ will degrade the material. I find very
few "extract audio from video" seem even to offer this option - and
where they do, they don't make it _clear_ that they do. [I want a GUI
one - I'm too set in my ways to mess with command lines. Sorry, ffmpeg
fans.] So many of them offer a choice of data rates, sample rates, and
mono/stereo - which to me seems obvious is doing some transcoding.

I currently use the Pazera utility
(http://www.pazera-software.com/produ...o-extractor/): may not be
the best, but (a) handles lots of video formats, (b) has a
clearly-identified "Try extract original audio stream" option. It's
clearly genuine, as when selected, it does it in the blink of an eye, so
no processing is being done. (It can also extract to raw .wav, though
obviously that will still contain any artefacts of the original
encoding.)

However, whenever (I think) I do it on .mp4 videos (certainly the ones
from YouTube), it always produces .m4a files. I had begun to think this
was a quirk of the Pazera software, but I recently did it on a video
file I'd got from somewhere other than YouTube (can't remember if it was
..mp4), and it produced a .mp3 file.

So is .m4a an intrinsic part of .mp4?

(And anyone care to suggest another versatile audio extractor that has a
clear don't-transcode option?

Regards, John


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  #2  
Old October 17th 18, 04:41 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
Frank Slootweg
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Posts: 1,226
Default audio extraction: do .mp4 videos always contain .m4a audio?

"J. P. Gilliver (John)" wrote:
[...]

However, whenever (I think) I do it on .mp4 videos (certainly the ones
from YouTube), it always produces .m4a files. I had begun to think this
was a quirk of the Pazera software, but I recently did it on a video
file I'd got from somewhere other than YouTube (can't remember if it was
.mp4), and it produced a .mp3 file.

So is .m4a an intrinsic part of .mp4?


File extensions are meaningless and irrelevant! They are only of some
use to software which is too stupid to look *in* the file to see what
*container* is used and which *encoding* is used for the video and audio
*in* that container.

Example: Take an (Apple) QuickTime file:

- probably has a .MOV extension
- probably has a MPEG4 container
- container might contain:
video: AVC encoding
audio: PCM encoding

So this file has a MPEG4 *container*, but the *encoding* is *not*
MPEG4!

Another example: One of my files which has a .mp4 extension:

- has a MPEG4 container with:
video: H.264 encoding
audio: LC-AAC encoding

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.

So I advise to check which audio *encoding* is used in both your
(video+audio) input file and (audio) output file and - at least at
first - not pay much/any attention to the file extensions.

Something as simple as VLC should be able to tell you that.

(And anyone care to suggest another versatile audio extractor that has a
clear don't-transcode option?


I've not done this for some time, but I think that MediaCoder [1] and
SUPER [2] can do this. MediaCoder is a transcoder, but I think it can
also just extract.

Good luck.

[1] http://www.mediacoderhq.com

[2] Is SUPER still alive?
  #3  
Old October 17th 18, 05:45 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
Bill in Co
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Posts: 1,927
Default audio extraction: do .mp4 videos always contain .m4a audio?

J. P. Gilliver (John) wrote:
I sometimes want to extract just the audio from a video clip (e. g. so I
can play it on my SatNav/GPS [I have an old one that doubles as an audio
player; I gather modern ones don't do that!], or just because the video
is static or irrelevant).

I would very much prefer to extract the _original_ audio stream:
although _I_ am unlikely to hear the difference, the purist in me feels
that any transcoding _in theory_ will degrade the material. I find very
few "extract audio from video" seem even to offer this option - and
where they do, they don't make it _clear_ that they do. [I want a GUI
one - I'm too set in my ways to mess with command lines. Sorry, ffmpeg
fans.] So many of them offer a choice of data rates, sample rates, and
mono/stereo - which to me seems obvious is doing some transcoding.

I currently use the Pazera utility
(http://www.pazera-software.com/produ...o-extractor/): may not be
the best, but (a) handles lots of video formats, (b) has a
clearly-identified "Try extract original audio stream" option. It's
clearly genuine, as when selected, it does it in the blink of an eye, so
no processing is being done. (It can also extract to raw .wav, though
obviously that will still contain any artefacts of the original
encoding.)

However, whenever (I think) I do it on .mp4 videos (certainly the ones
from YouTube), it always produces .m4a files. I had begun to think this
was a quirk of the Pazera software, but I recently did it on a video
file I'd got from somewhere other than YouTube (can't remember if it was
.mp4), and it produced a .mp3 file.

So is .m4a an intrinsic part of .mp4?

(And anyone care to suggest another versatile audio extractor that has a
clear don't-transcode option?

Regards, John


M4A is a file extension for an audio file encoded with advanced audio coding
(AAC). I don't believe most mp4 files have mp3 audio tracks. If you don't
want any transcoding (to mp3), I think you're stuck with playing aac audio
files, which some players can do. It is possible, however, to download a mp4
file and extract the aac track without any transcoding.


  #4  
Old October 17th 18, 09:05 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
VanguardLH[_2_]
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Posts: 10,881
Default audio extraction: do .mp4 videos always contain .m4a audio?

Frank Slootweg wrote:

Another example: One of my files which has a .mp4 extension:

- has a MPEG4 container with:
video: H.264 encoding
audio: LC-AAC encoding

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.


H.264 = MPEG-4 part 10 AVC
https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC

There is also:

H.263 = MPEG-4 part 2
https://en.wikipedia.org/wiki/MPEG-4_Part_2

There are multiple naming conventions for the same coding and
compression format: MPEG, ISO/IEC, and ITU-T. See:

https://en.wikipedia.org/wiki/MPEG-4

AAC is the successor to MP3 and probably why it shows up in an MPEG
container file. Not sure why you thought an .mp4 container must or
hints at MP3 for audio encoding.

LC-AAC, AAC-LC = MPEG-2 ACC aka MPEG-2 part 7 aka ISO/IEC 13818-7.
  #5  
Old October 17th 18, 09:13 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
JJ[_11_]
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Posts: 744
Default audio extraction: do .mp4 videos always contain .m4a audio?

On 17 Oct 2018 15:41:02 GMT, Frank Slootweg wrote:

So this file has a MPEG4 *container*, but the *encoding* is *not*
MPEG4!

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.


To make things clear...

It's true that file extension is irrelevant to the file contents, but it
serves similar to MIME type. Both file extension and MIME type don't
guarantee the type of file contents. Web servers and browsers rely heavily
on MIME type, but MIME type itself relies heavily on file extension. So, if
any is incorrectly translated/mapped, a binary file might end up being
served as text in the browser. Both file extension and MIME type can be used
as a hint to speed up the content type detection. It's up to the software
whether to use it as part of their content detection, or not.

And the number 4 in the MPEG4 container doesn't represent the version number
of the video/audio streams within the container. It's merely the version
number of the media container format. Each video/audio stream has its own
version which is encoding specific (or format specific).
  #6  
Old October 17th 18, 09:14 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
Frank Slootweg
external usenet poster
 
Posts: 1,226
Default audio extraction: do .mp4 videos always contain .m4a audio?

VanguardLH wrote:
Frank Slootweg wrote:

Another example: One of my files which has a .mp4 extension:

- has a MPEG4 container with:
video: H.264 encoding
audio: LC-AAC encoding

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.


H.264 = MPEG-4 part 10 AVC
https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC


Yes, I know, but that just re-enforces my point. .mp4 and MPEG4 are
*ambiguous* terms. If you have a ".mp4 file" or a "MPEG4 file", you
still don't have a clue about its encodings.

[Left for completeness (Been there, done that, got the T-shirt.):]

There is also:

H.263 = MPEG-4 part 2
https://en.wikipedia.org/wiki/MPEG-4_Part_2

There are multiple naming conventions for the same coding and
compression format: MPEG, ISO/IEC, and ITU-T. See:

https://en.wikipedia.org/wiki/MPEG-4

AAC is the successor to MP3 and probably why it shows up in an MPEG
container file. Not sure why you thought an .mp4 container must or
hints at MP3 for audio encoding.

LC-AAC, AAC-LC = MPEG-2 ACC aka MPEG-2 part 7 aka ISO/IEC 13818-7.

  #7  
Old October 17th 18, 09:25 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
JJ[_11_]
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Posts: 744
Default audio extraction: do .mp4 videos always contain .m4a audio?

On Thu, 18 Oct 2018 03:13:33 +0700, JJ wrote:

And the number 4 in the MPEG4 container doesn't represent the version number
of the video/audio streams within the container. It's merely the version
number of the media container format. Each video/audio stream has its own
version which is encoding specific (or format specific).


However, AFAIK, an MPEG media (i.e. video+audio) container is for containing
MPEG video format only. i.e. it can not contain e.g. DVI, VP8, Windows Video
format. Audio format is more relaxed but AFAIK (correct me if I'm wrong),
there's still a limit on which audio formats are supported by the MPEG media
container.
  #8  
Old October 17th 18, 09:38 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
Ken Blake[_5_]
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Posts: 2,221
Default audio extraction: do .mp4 videos always contain .m4a audio?

On Thu, 18 Oct 2018 03:13:33 +0700, JJ wrote:

On 17 Oct 2018 15:41:02 GMT, Frank Slootweg wrote:

So this file has a MPEG4 *container*, but the *encoding* is *not*
MPEG4!

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.


To make things clear...

It's true that file extension is irrelevant to the file contents,




It's not really irrelevant to the file contents. It's very relevant;
it describes what the file contents are.

Yes, that description can be incorrect, and that's probably what you
meant. But it's seldom incorrect, so it's far from being irrelevant.
  #9  
Old October 17th 18, 10:19 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
Frank Slootweg
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Posts: 1,226
Default audio extraction: do .mp4 videos always contain .m4a audio?

Ken Blake wrote:
On Thu, 18 Oct 2018 03:13:33 +0700, JJ wrote:

On 17 Oct 2018 15:41:02 GMT, Frank Slootweg wrote:

So this file has a MPEG4 *container*, but the *encoding* is *not*
MPEG4!

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.


To make things clear...

It's true that file extension is irrelevant to the file contents,


It's not really irrelevant to the file contents. It's very relevant;
it describes what the file contents are.

Yes, that description can be incorrect, and that's probably what you
meant. But it's seldom incorrect, so it's far from being irrelevant.


It was actually *my* comment (That's what you get for killfiling
people for the wrong 'reasons'! :-) c.q. :-( [1] [2]).

The description *can* be correct for some simple cases, but - as I
have explained - the description is not and cannot be unambigous,
because there are too many variables to be put in just three characters.

Example: .mp4 probably implies some form of MPEG4 video encoding, but
*which* one, of the several ones? And *which* audio encoding does it
use?

[1] If you quote an attribution line with my name and quote my text,
then why don't you respond to me?

[2] Have you seen my and Paul's solutions to your killfiling problem?
  #10  
Old October 17th 18, 10:59 PM posted to alt.windows7.general
Retroman[_3_]
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Posts: 12
Default audio extraction: do .mp4 videos always contain .m4a audio?

On Wed, 17 Oct 2018 14:30:04 +0100, "J. P. Gilliver (John)"
wrote:

I sometimes want to extract just the audio from a video clip (e. g. so I
can play it on my SatNav/GPS [I have an old one that doubles as an audio
player; I gather modern ones don't do that!], or just because the video
is static or irrelevant).

I would very much prefer to extract the _original_ audio stream:
although _I_ am unlikely to hear the difference, the purist in me feels
that any transcoding _in theory_ will degrade the material. I find very
few "extract audio from video" seem even to offer this option - and
where they do, they don't make it _clear_ that they do. [I want a GUI
one - I'm too set in my ways to mess with command lines. Sorry, ffmpeg
fans.] So many of them offer a choice of data rates, sample rates, and
mono/stereo - which to me seems obvious is doing some transcoding.

I currently use the Pazera utility
(http://www.pazera-software.com/produ...o-extractor/): may not be
the best, but (a) handles lots of video formats, (b) has a
clearly-identified "Try extract original audio stream" option. It's
clearly genuine, as when selected, it does it in the blink of an eye, so
no processing is being done. (It can also extract to raw .wav, though
obviously that will still contain any artefacts of the original
encoding.)

However, whenever (I think) I do it on .mp4 videos (certainly the ones
from YouTube), it always produces .m4a files. I had begun to think this
was a quirk of the Pazera software, but I recently did it on a video
file I'd got from somewhere other than YouTube (can't remember if it was
.mp4), and it produced a .mp3 file.

So is .m4a an intrinsic part of .mp4?


No, M4a is a container format created by Apple to hold AAC audio.
YouTube recommends uploading AAC audio in MP4 containers. When
those containers have an AAC component, most audio extractors can
either output the raw AAC as a file or "repackage" it into an M4a
container. The latter is very desirable as far more devices can
play M4a than raw AAC, and M4a supports a full range of metatags,
which AAC does not.

When you play an M4a file, you are in fact playing the original
AAC audio. In other words, no transcoding was done, only
"repackaging". That means that there is no degradation.

I would very much prefer to extract the _original_ audio stream


I'm with you on this but it's worth noting that youTube itself
often re-encodes video submissions. Thus the audio that we hear
on youTube may have a lower bitrate than it did in the video as
submitted. That means that the quality may be less even though
the format is the same as the original.
  #11  
Old October 17th 18, 11:06 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
Paul[_32_]
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Posts: 11,873
Default audio extraction: do .mp4 videos always contain .m4a audio?

Ken Blake wrote:
On Thu, 18 Oct 2018 03:13:33 +0700, JJ wrote:

On 17 Oct 2018 15:41:02 GMT, Frank Slootweg wrote:
So this file has a MPEG4 *container*, but the *encoding* is *not*
MPEG4!

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.

To make things clear...

It's true that file extension is irrelevant to the file contents,




It's not really irrelevant to the file contents. It's very relevant;
it describes what the file contents are.

Yes, that description can be incorrect, and that's probably what you
meant. But it's seldom incorrect, so it's far from being irrelevant.


File extension .mp4 : On a Windows system, this binds the file
to a potential player application. You should not
use (or change) extensions, if the result will be
unpredictable. For example, if a Windows user
changes that to .txt , Notepad opens, and Notepad
shows a ton of binary gibberish, instead of a
video. That would be bad...

Container : MP4 is a container type.

https://en.wikipedia.org/wiki/MPEG-4_Part_14

"MPEG-4 Part 14 or MP4 is a digital multimedia container format
most commonly used to store video and audio"

Other examples of containers are AVI, MOV, MKV

https://en.wikipedia.org/wiki/Compar...tainer_formats

Codec : A container can support multiple CODEC (coder/decoder) types
A container can support a multitude of streams, requiring
a demux in the decoder chain to select individual streams.

It's probably possible, and reasonably easy, to run FFMPEG in
copy mode, and demux an MP4 and make an M4A (audio-only) of it. If you wanted.
And with no "loss" because of the copy mode. You would research
how to use FFMPEG as a demux... The next question would be,
what to do with the M4A. Maybe an iPod could play it. Or
maybe not.

*******

On a Linux system, the file extension is irrelevant. That's
because the object oriented launcher "sniffs" the file, rather than
trusting the extension. The "file" (sniffer) command, using /etc/magic,
contains identification capabilities indicating what the file contains.
Instead of a Text Editor opening, at least the Totem movie player
should open (even if, as it turns out, Totem doesn't have a
decoder that actually works). Sometimes, additional decoders
have to be installed, to help the movie player.

No purpose is served in Linux by telling a lie about the content,
so you would likely keep a representative extension on the file
anyway. If you wanted though, you could drop the pretense
entirely, and "starwars.vob" could be "starwars" if you wanted.
Whereas on a Windows system, it would bring up the "anonymous
program selector" dialog, the one that "does not remember your
selection" because the file type is anonymous, if you double
clicked a filename of "starwars" without an extension.

Paul
  #12  
Old October 17th 18, 11:19 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
Bill in Co
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Posts: 1,927
Default audio extraction: do .mp4 videos always contain .m4a audio?

Frank Slootweg wrote:
VanguardLH wrote:
Frank Slootweg wrote:

Another example: One of my files which has a .mp4 extension:

- has a MPEG4 container with:
video: H.264 encoding
audio: LC-AAC encoding

So this file has a .mp4 extension, but the video encoding is *not*
MPEG4 and the audio encoding is *not* MP3.


H.264 = MPEG-4 part 10 AVC
https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC


Yes, I know, but that just re-enforces my point. .mp4 and MPEG4 are
*ambiguous* terms. If you have a ".mp4 file" or a "MPEG4 file", you
still don't have a clue about its encodings.


Well yeah, I do have one at least one clue! If it's an mp4, it most likely
contains .aac audio, and not mp3. As for the video, that's another story
:-) (and hopefully it used.h264, and not one of the older compression
formats)

But one can find out what's inside by using a simple utility program like
MediaInfo.


  #13  
Old October 18th 18, 04:42 AM posted to alt.windows7.general,microsoft.public.windowsxp.general
J. P. Gilliver (John)[_4_]
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Posts: 2,679
Default audio extraction: do .mp4 videos always contain .m4a audio?

In message , Bill in Co
writes:
[]
M4A is a file extension for an audio file encoded with advanced audio coding
(AAC). I don't believe most mp4 files have mp3 audio tracks. If you don't
want any transcoding (to mp3), I think you're stuck with playing aac audio
files, which some players can do. It is possible, however, to download a mp4
file and extract the aac track without any transcoding.

Yes, I think that's what Pazera is doing. I just hadn't realised that
..m4a was AAC; I'd thought it was an obscure format.

I take it that .aac as a file extension isn't used much (at all?).
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

(Petitions - at least e-petitions - should collect votes both for and
against, if they're going to be reported as indicative of public
opinion. If you agree, please click below, unless you already have.) [UK only]
https://petition.parliament.uk/petit...BYobumelL9J54c

There's only so much you can do... with gravel.
- Charlie Dimmock, RT 2016/7/9-15
  #14  
Old October 18th 18, 06:42 AM posted to alt.windows7.general,microsoft.public.windowsxp.general
Bill in Co
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Posts: 1,927
Default audio extraction: do .mp4 videos always contain .m4a audio?

J. P. Gilliver (John) wrote:
In message , Bill in Co
writes:
[]
M4A is a file extension for an audio file encoded with advanced audio
coding (AAC). I don't believe most mp4 files have mp3 audio tracks. If
you don't want any transcoding (to mp3), I think you're stuck with
playing aac audio files, which some players can do. It is possible,
however, to download a mp4 file and extract the aac track without any
transcoding.

Yes, I think that's what Pazera is doing. I just hadn't realised that
.m4a was AAC; I'd thought it was an obscure format.

I take it that .aac as a file extension isn't used much (at all?).


No, I wouldn't quite take it that way :-) I think it's the default audio
extension for anything Apple related (well, that, and .m4a). (think of
iTunes, for example).

But for us PC users, I think mp3 is much more commonly used. I don't have
any interest in iTunes, thank you very much. :-)


  #15  
Old October 18th 18, 02:12 PM posted to alt.windows7.general,microsoft.public.windowsxp.general
J. P. Gilliver (John)[_4_]
external usenet poster
 
Posts: 2,679
Default audio extraction: do .mp4 videos always contain .m4a audio?

In message , Bill in Co
writes:
J. P. Gilliver (John) wrote:
In message , Bill in Co
writes:
[]
M4A is a file extension for an audio file encoded with advanced audio
coding (AAC). I don't believe most mp4 files have mp3 audio tracks. If
you don't want any transcoding (to mp3), I think you're stuck with
playing aac audio files, which some players can do. It is possible,
however, to download a mp4 file and extract the aac track without any
transcoding.

Yes, I think that's what Pazera is doing. I just hadn't realised that
.m4a was AAC; I'd thought it was an obscure format.

I take it that .aac as a file extension isn't used much (at all?).


No, I wouldn't quite take it that way :-) I think it's the default audio
extension for anything Apple related (well, that, and .m4a). (think of


So what is the _difference_ between (files ending in) .aac and .m4a then
- if there is one?

iTunes, for example).


I'd rather not (-:. From what I've seen, it takes over, unless you spend
time keeping it in check.

But for us PC users, I think mp3 is much more commonly used. I don't have
any interest in iTunes, thank you very much. :-)

Me too. I have seen the Apple Kool-aid, and I can see that it tastes
nice; I prefer more to keep control of my machine, though.

--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

(Petitions - at least e-petitions - should collect votes both for and
against, if they're going to be reported as indicative of public
opinion. If you agree, please click below, unless you already have.) [UK only]
https://petition.parliament.uk/petit...BYobumelL9J54c

It is important to write so that you can be understood. It is far more
important to write so that you cannot be misunderstood.
 




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