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15th October 2010, 22:39 | #1 | Link |
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Why there's no LATM AAC demuxer/converter?
Almost a year ago I got a DTV capture device (ISDB-Tb) to be able to watch the first digital broadcasts, since DTV standard was adopted in my country in September 2009.
From the beginning, the programs have been broadcasted with HE-AAC audio in LATM container, forcing me to decode it through Winamp to WAV and then back to HE-AAC without LATM (LATM HE-AAC → WAV → HE-AAC). Searching in the forum, I've realized that LATM has always been a problem when decoding since 2007, and after 3 years the problem seems to remain in the same way. I asked my man Google to find a way to demux LATM HE-AAC to raw AAC or to ADTS (the most popular container) and it finds nothing but this webpage with CLI programs that convert from LATM to ADTS and to raw AAC. When I try to convert a LATM stream, I get access violation error. So, I'm still reencoding LATM HE-AAC audio. Then, the only thing I can do (since I'm not a programmer) is to wonder why, after 3 years, there's still no LATM AAC demuxer/converter. Saludos By ALEX-KID |
17th October 2010, 22:42 | #3 | Link |
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Ok, I understand that. However, there are some LATM filters that works to get audio from speakers. For example, the Elecard LATM demultiplexer (bundled in Elecard Codec SDK G4) only connects to audio decoders, it cannot connect to file writers or something like that. Maybe (I really don't know) it could be possible to write a CLI that write raw or ADTS AAC data to a file using that demultiplexer. On the other hand, Igor Janos (taken from his blog at Monogram AAC decoder 0.9.6.0 thread) wrote on July 4, 2009, "As for the LATM -> ADTS conversion… I’m currently not aware of any filter/software that would do this. However the AAC decoder contains a routine that performs this when feeding the libfaad library with AAC data so I suppose it might be possible to write just a simple LATM->RAW/ADTS convertor filter." But there's still no tool like this.
My only hope (very blind, since I don't have programming skills) were the programs that I found on the webpage quoted in the first message. They look very simple, CLI and small, but I don't know if they are missing a little thing or are written completely bad. All I can say is that they don't work with my captures. I don't know if LATM is a "very ugly format", but when I search through the Internet I see much information about it, so I can't understand why there's no LATM demuxer or converter. Speccially if Igor says it could be done. Saludos By ALEX-KID |
18th October 2010, 22:32 | #6 | Link |
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Out of interest... Are you able to provide any samples?
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19th October 2010, 16:23 | #7 | Link |
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Here it is a TS sample containing LATM AAC audio (54.91 Mb)
http://www.mediafire.com/?l0qvuwl53ne18e3 And here it is the LATM encapsulated audio stream from the same file above (404.2 Kb). http://www.mediafire.com/?99128a2ntkd0tam Thank you for your interest. Saludos By ALEX-KID |
24th October 2010, 12:05 | #8 | Link |
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Thanks for the samples Alex...
Essentilly I wanted to know if my Xtreamer hardware players supported playback of such audio streams. And yes they do
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26th October 2010, 18:09 | #10 | Link |
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I've managed to do this with VLC and eac3to.
They also use LATM here in Denmark and I had a lot of trouble with recordings from our HD channel. VLC can play these files as long as they are muxed in a ts or mp4 container, but I found out that if you remuxed a ts file with VLC it would strip the LATM bit packing from the stream. First I would use eac3to with the -demux parameter to demux the ts file and get the raw audio stream as a file. So then I use a command like this to remux the .aac file back into a transportstream and VLC will do it's thing. Code:
vlc.exe -I dummy aud_latm.aac --sout #std{access=file,mux=ts,dst="aud_nolatm.ts"} vlc://quit Hope this helps |
27th October 2010, 00:45 | #11 | Link |
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Thanks Vippe.
VLC seems work with my two latm samples. Also work using: mux=mp4,dst="aud_nolatm.mp4" Maybe better? The mp4 is accepted directly in MkvMerge, tsMuxeR and YAMB With YAMB (and Foobar2000) the TVN aac in .ts is showed like AAC Main 24KHz, the .mp4 like AAC LC 48 KHz
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BeHappy, AviSynth audio transcoder. Last edited by tebasuna51; 27th October 2010 at 01:09. |
27th October 2010, 09:48 | #12 | Link |
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Which version of VLC player are you guys using?
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27th October 2010, 11:18 | #14 | Link |
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Bummer...
I've tried VLC v1.1.4 with Alex-Kid's 54.91MB sample and got a file containing 0 bytes
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27th October 2010, 12:16 | #15 | Link |
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You need extract the aac first (404 KB), with eac3to or DGAVCIndex, like Vippe say:
"First I would use eac3to with the -demux parameter to demux the ts file and get the raw audio stream as a file." Edit: I think Alex-Kid supply also the aac_latm extracted.
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BeHappy, AviSynth audio transcoder. Last edited by tebasuna51; 27th October 2010 at 12:19. |
8th January 2011, 22:04 | #17 | Link | |
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Quote:
_
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8th January 2011, 23:32 | #18 | Link |
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example:
video source: h264 in .mp4 (no audio) audio source: .aac destination: .mp4 _ N.B. iPad sucks at editing long posts.... _
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30th April 2013, 21:09 | #20 | Link |
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I have been looking for latm aac converter as well for long time, and I know there is code for it on ffmpeg, it can read latm aac files properly however there is unfortunately no option to use it to output just the non latm aac audio without re-compressing it (what I'm looking for... it seems also that tvheadend guys have been able to use ffmpeg latm parser to do such a converter but just for realtime mkv recordings), I did suggested an enhancement for ffmpeg so that latm decoder could be added as a possible bitstream filter, possible allowing the latm decode on 'copy' stream without re-compressing audio:
https://ffmpeg.org/trac/ffmpeg/ticket/2439 (if anyone else interested please vote it/comment there, maybe someone picks the task if there is more people interested on it ) |
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