If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Rate Thread | Display Modes |
#1
|
|||
|
|||
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 (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 citizens only] -- J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf https://petition.parliament.uk/petit...BYobumelL9J54c Back then, many radio sets were still in black and white. - Eddie Mair, radio presenter, on "PM" programme reaching 40; in Radio Times, 3-9 April 2010 |
Ads |
#2
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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. |
|
Thread Tools | |
Display Modes | Rate This Thread |
|
|