About the “libxaac” project

[jiangzemin-xudamin]

Hey, Martin，
I recently noticed a project called “libxaac” on GitHub, I wonder if it could be a better alternative to “exhale”?
https://github.com/ittiam-systems/libxaac

[MartinEesmaa]

Hey, @jiangzemin-xudamin! It is good to see you back there after questions by issuing. :)

I tried using libxaac which is good alternative license to fdk-aac non-free license.
However, the problem is only for xHE-AAC does not support AAC ADTS output which I can't decode probably.

xaacenc -ifile:sine_2ch.wav -ofile:sine_2ch_aot_4112.es -adts:1 -br:64000
 -aot:42
-ifile:sine_2ch.wav -ofile:sine_2ch_aot_4112.es -adts:1 -br:64000 -aot:42
Stream bit rate = 64000

 loudness level : -6.761214
 sample_peak_level : -1.938333
                       ITTIAM SYSTEMS PVT LTD, BANGALORE
                             http:\\www.ittiam.com
                                IXHEAACE : V2.0


************************************************************************************************

Parameters Taken:

AOT : 42 - USAC
USAC Codec Mode : Not Enabled
Harmonic SBR : 0
High quality esbr : 0
Complex Prediction Flag : 0
TNS Flag : 1
Core-coder framelength index (Unsupported configuration, enabling 2:1 eSBR) : 3
Noise Filling Flag : 0
Use ADTS Flag (Invalid config value, setting to default) : 0
Use TNS Flag : 1
Bitrate : 64000 bps
Frame Length : 1024
Sampling Frequency : 48000 Hz
************************************************************************************************

Frames Processed [232]

I tried set flag of ADTS from 0 to 1 when encoding USAC and refuses which encodes to raw audio file encoded lossy without ADTS/MP4 mux.

Tried decode (first error):

xaacdec -ifile:sine_2ch_aot_4112.es -ofile:sine_2ch_aot_4112.ts3
-ifile:sine_2ch_aot_4112.es -ofile:sine_2ch_aot_4112.ts3
                       ITTIAM SYSTEMS PVT LTD, BANGALORE
                             http:\\www.ittiam.com
                         IA_XHEAAC_DEC_MSVC Rev: 1.41

Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
non fatal error: Ittiam xheaac_dec: Execution: : LTP data found, not supported
fatal error: Ittiam xheaac_dec: Initialization: : No. of channels in stream greater than max channels defined

So I can't decode raw audio frame except ADTS flag works for AAC LC container... I will try to figure out to decode raw audio frames of .ES file.

UPDATE: I think I finally got it to decode:

xaacdec -ifile:sine_2ch_aot_223.es -imeta:sine_2ch_aot_223.txt -mp4:1 -ofile:sine_2ch_aot_21.wav

Log:

xaacdec -ifile:sine_2ch_aot_223.es -imeta:sine_2ch_aot_223.txt -mp4:1 -ofile:sine_2ch_aot_21.wav
-ifile:sine_2ch_aot_223.es -imeta:sine_2ch_aot_223.txt -mp4:1 -ofile:sine_2ch_aot_21.wav
                       ITTIAM SYSTEMS PVT LTD, BANGALORE
                             http:\\www.ittiam.com
                         IA_XHEAAC_DEC_MSVC Rev: 1.41

Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: UPSAMPLING FACTOR 2 or 8/3
TOTAL FRAMES : [  234]
Channel Mode: NONE_OF_THESE or MULTICHANNEL
SBR Mode: NOT_PRESENT

It requires metadata file of text and mp4 flag to decode from USAC to WAV file. I tested and it worked, but it sounded buffer weird glitches.

• Martin Eesmaa

[jiangzemin-xudamin]

@MartinEesmaa ! I'm glad you're returning to your project and thank you for helping me test the usability of libxaac.

However, the problem is only for xHE-AAC does not support AAC ADTS output which I can't decode probably.

So, I wonder if it is theoretically possible to modify the MPV player to support AAC ADTS?

[jiangzemin-xudamin]

It requires metadata file of text and mp4 flag to decode from USAC to WAV file. I tested and it worked, but it sounded buffer weird glitches.

It's a shame, probably it will still take some time before it becomes a full-fledged audio codec, looking forward to its merger with FFMPEG!

[jiangzemin-xudamin]

I was wondering if you can send the compiled libxaac binaries to your vvceasy project? Just like the previous UVG266 binaries.