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AAC-HE realtime decoder for Windows?, Looking for a aac-he Directshow decoder
knutinh
post Dec 4 2007, 14:46
Post #1





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Posts: 569
Joined: 1-November 06
Member No.: 37047



Here in Norway, digital terrestrial tv transmissions have recently started.

Transmissions are in h264 (potentially 720p, but in practice 576i due to bandwidth) and AAC-HE with LOAS/LATM.

http://www.dvbviewer.info/forum/index.php?...90&start=90
http://forum.team-mediaportal.com/he_aac_s...b_t-t31159.html
ftp://ftp.terratec.de/Receiver/TerraTec_HomeCinema/Beta/

Problem is, such decoders are nowhere to be found, and Norway is only a small country in the big picture. It seems that a lot of people wants this, but no one wants to deliver. Are there any open-source projects that could be used? Anyone know why this seems to be so difficult? Licensing issues?

Dvbviewer can playback AAC-HE channels, but the decoder that actually is needed is not available for end-users! Terratec has a working decoding application, but it only works with a single dvb receiver.

QUOTE
...
After some trial and error, additional coding and some help from TerraTec I managed to let DVBViewer play HE AAC audio with the Cyberlink decoder. However, it's still a bit buggy. It has difficulties to find a starting point in the stream, and it doesn't perform SBR upsampling resp. high frequency reconstruction. The output samplerate should be 48 khz in case of Norwegian AAC, but it's 24 khz. So Cyberlink will have to work on it a bit more.
...


http://www.codingtechnologies.com./news/as...rwayDVB_eng.pdf

QUOTE
Norway’s DVB-T selects Coding Technologies’ MPEG-4 aacPlus audio
codec in world’s first deployment for Digital Terrestrial Television
Combination of aacPlus/DTS transcoding guarantees backwards
compatibility to existing installed base of home theatre systems
Las Vegas, Nev., NAB 2007, and Nuernberg, Germany, April 16th 2007
— Coding Technologies, the leading provider of audio compression for
mobile, digital broadcasting and the Internet, today announced that its
audio compression technology has been selected by Norway’s digital
terrestrial platform. The deployment of Coding Technologies’ advanced
aacPlus audio codec for stereo and surround sound is the first of its kind in
digital terrestrial HD (High Definition) and SD (Standard Definition) TV
broadcasting and sees the Norwegian DVB-T platform the first to benefit
from the most efficient use of available spectrum, enabling broadcasters to
deliver more TV programming at reduced transmission costs.
...


http://www.dvb.org/technology/bluebooks/a0...1154.v1.8.1.pdf
QUOTE
4.1.6.1 stream_id and stream_type
Encoding: Elementary streams shall be identified by stream_id and stream_type in accordance with
ITU-T Recommendation H.222.0 | ISO/IEC 13818-1 [1], tables 2-18 and 2-29.
For VC-1 Bitstreams, the following applies:
Encoding: Elementary streams shall be identified by stream_id (with the extension mechanism) and
stream_type in accordance with SMPTE RP 227 [22].
NOTE: For VC-1 Bitstreams, the value of stream_type shall be set to 0xEA.
Decoding: IRDs shall be able to accept bitstreams which contain these encoded values.
For MPEG-4 AAC, MPEG-4 HE AAC and MPEG-4 HE-AAC v2 audio streams, the following applies:
Encoding: The value of the stream_id field for LATM/LOAS formatted MPEG-4 AAC, MPEG-4 HE AAC and
MPEG-4 HE AAC v2 packetized elementary streams shall be 110x xxxx, where each x can be
either 0, or 1. The value of stream_type for MPEG-4 AAC, MPEG-4 HE AAC and MPEG-4 HE
AAC v2 packetized elementary streams shall be 0x11 (indicating ISO/IEC 14496-3 [17] Audio
with the LATM transport syntax).
Decoding: This field shall be read by the IRD, and the IRD shall interpret this field in accordance with
MPEG systems syntax.

QUOTE
6.4.1 LATM/LOAS formatting
The MPEG-4 HE AAC or HE AAC v2 elementary stream data shall be first encapsulated in the LATM multiplex format
according to ISO/IEC 14496-3 [17]. The AudioMuxElement() multiplex element format shall be used.
DVB BlueBook A001 Rev. 7
68
The LATM formatted MPEG-4 HE AAC or HE AAC v2 elementary stream data shall be encapsulated in the LOAS
transmission format according to ISO/IEC 14496-3 [17]. The AudioSyncStream() version shall be used.
AudioSyncStream() adds a sync word to the audio stream to allow for synchronization.Semantics: The semantics of the
AudioMuxElement() and AudioSyncStream() formatting are described in ISO/IEC 14496-3 [17].
Encoding: The MPEG-4 HE AAC and HE AAC v2 elementary streams shall be formatted with
AudioMuxElement() LATM multiplex format, and AudioSyncStream() LOAS transmission
format.
The following limitations to the LATM multiplex shall apply;
 numLayer shall be "0", as no scalable profile is used;
 numProgram shall be "0", as there is only one audio program per LATM multiplex;
 numSubFrames shall be "0", as there is only one PayloadMux() (access unit) per LATM
AudioMuxElement();
 allStreamsSameTimeFraming shall be "1", as all payloads belong to the same access
unit.
Decoding: These formats shall be read by the IRD, and the IRD shall interpret these formats in accordance
with MPEG-4 audio syntax.


http://www.digital-everywhere.com/en/alcms...?sid=1190404664

QUOTE
Digital Terrestrial TV ( DVB-T ) receiver for notebook and multimedia computer

NEW!!!

FireDTV T/CI works now with the
Free To Air channels from RiksTV in Norway
...
- MPEG4 / H.264 Software decoders

- LATM AAC audio decoders for DVB-T in Norway


-k

This post has been edited by knutinh: Dec 4 2007, 15:24
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menno
post Dec 4 2007, 15:45
Post #2


Nero MPEG4 developer


Group: Developer (Donating)
Posts: 1218
Joined: 11-October 01
From: LA
Member No.: 267



LOAS/LATM is a container, so it's the job of the parser filter to parse it and send the raw AAC data to the HE AAC decoder.
AFAIK latest Nero versions should have such a parser filter.
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