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14th June 2004, 12:53 | #1 | Link |
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HowTo find out which codecs where used to create a MP4 file
as in MP4 all streams are "equal", no matter what codec was used to create them, its not that easy to find out which codec was used for the creation of a specific MP4 file, but its possible:
MPEG-4 ASP Video: in AVI a so called FourCC System is used to describe the stored content (the fourcc normally tells the used encoder (unless someone changed it) and allows only specifc decoders to connect to a specific fourcc (DivX5 decoder by default connects to the DIVX/DX50 fourcc, XviD decoder to the XVID fourcc aso...)) in MP4 for storing MPEG-4 Video nothing comparable to a FourCC exists! why should it exist? all streams are MPEG-4 compliant anyways (DivX5 = MPEG-4 = XviD) so why mark them as "DIVX", "XVID" aso...? for example are MP3 audio files marked using a fourcc? allowing only specific MP3 decoders to connect to them? wouldnt make much sense, right? therefore in MP4 all MPEG-4 (A)SP video streams are equally marked as "mp4v" now how to find out what encoder was used? most mpeg-4 asp encoders mark in the video bitstream (not in the container), in the so called "user data"/"bitstream description", that the stream was encoded by them this info can be read out by the nice MPEG4VOL tool, which is part of the MPEG4IP toolset (thanks to DeXT, you can download it here. beaware the version on rarewares is outdated and will not work correctly!). mpeg4vol is a commandline tool and therefore you have to feed it with the following commandline (copy it to a .txt file, place it in the same folder as mpeg4vol.exe, rename the .txt to .bat and execute it): Code:
mpeg4vol.exe "c:\path to\file.mp4" Code:
XviD: XviD0029 ("DivX999b000p" indicates packed bitstream, "C" cartoon mode) DivX5: DivX503b1031 ("p" indicates packed bitstream has been used) ffmpeg/ffvfw/ffdshow: FFmpeg0.4.8b4684 3ivx: 3ivx@— NeroDigital: em4v 4.1.4.14 Quicktime/Sorenson/DivX4: these MPEG-4 encoders dont seem to set a bitstream info dont look at "FourCC" cause it most likely will not be the correct one, have a look at "Codec", which shows the bitstream description on the bitstream level (DRF Analyser simply displays the used FourCC again (like DIVX, which doesnt mean that DivX5 was used of course) if no bitstream info has been set (like with Quicktime/Sorenson/DivX4 streams)) MPEG-4 AAC Audio: to my knowledge the current AAC encoders dont set an user data comparable to the video codecs, or at least no tool exists to read it out, but its possible already to identify nero and faac encoded streams: open up the MP4 containing the nero/faac aac track in the foobar audio player, right click -> properties -> technical info on files encoded with newer versions of faac/nero there will be displayed which version was used to encode the stream. with files outputted by other encoders nothing will be displayed this is not a good solution, i know, and it also seems that this info gets lost if you export to .aac and transmux to another .mp4 MP3 Audio as its the case for AAC audio there also is no 100% correct method to get to know what codec was used to encode a MP3 stream, but there is a smart tool existing which is able to detect the encoder most of the time correctly: EncSpot it is really a must have tool for every MP3 freak
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Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau) I know, that I know nothing (Socrates) MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide) Ogg Theora | Ogg Vorbis use WM9 today and get Micro$oft controlling the A/V market tomorrow for free Last edited by bond; 26th June 2004 at 00:24. |
15th June 2004, 10:40 | #2 | Link | |
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Re: HowTo find out which codecs where used to create a MP4 file
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15th June 2004, 11:24 | #3 | Link | |
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Re: Re: HowTo find out which codecs where used to create a MP4 file
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how is it stored? itunes tags?
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Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau) I know, that I know nothing (Socrates) MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide) Ogg Theora | Ogg Vorbis use WM9 today and get Micro$oft controlling the A/V market tomorrow for free |
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15th June 2004, 14:19 | #4 | Link |
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Yes,
dBpowerAMP seems to be able to identify the many different types of AAC encoder used and sometimes the version type! It's not perfect though. And ofcourse the detailed information is lost as soon as you demux content out and then back into the container. Cheers EDIT: Links to images re-established
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Last edited by SeeMoreDigital; 18th February 2005 at 10:57. |
15th June 2004, 17:11 | #5 | Link | ||
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Re: Re: Re: HowTo find out which codecs where used to create a MP4 file
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@SeeMoreDigital: This seems to be from dBpowerAMP... |
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15th June 2004, 18:36 | #6 | Link | |
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Quote:
Previous post altered accordingly... Cheers
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15th June 2004, 19:20 | #7 | Link | |
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its surely stored in udta atom, as its lost when extracting to .aac and remuxing to .mp4
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Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau) I know, that I know nothing (Socrates) MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide) Ogg Theora | Ogg Vorbis use WM9 today and get Micro$oft controlling the A/V market tomorrow for free |
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15th June 2004, 20:33 | #8 | Link | |
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Quote:
Here are a couple of examples from Foobar2000: - Cheers EDIT: Link to image re-established
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Last edited by SeeMoreDigital; 21st April 2005 at 16:30. |
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18th February 2005, 10:13 | #9 | Link | |
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Re: HowTo find out which codecs where used to create a MP4 file
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18th February 2005, 12:09 | #10 | Link |
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?
How does a FourCC say anything about quality? With the right/wrong settings, you can virtually let any codec look better than another. Bitrate being the easiest of settings to influence that. Not to mention that a FCC is way to easy to change to count as any sort of reliable information. |
18th February 2005, 12:11 | #11 | Link | |
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