[Ffmpeg-user] Ultra-low-bitrate audio codec?

[Michel Bardiaux]

The lowest possible bitrate I could achieve was GSM at 13kbits. Is there
some codec in lavc that can go below that? (Sample command would be
welcome). TIA.

[Michel Bardiaux]

Post by Michel Bardiaux
The lowest possible bitrate I could achieve was GSM at 13kbits. Is there
some codec in lavc that can go below that? (Sample command would be
welcome). TIA.

Someone suggested to me (off list) amr_nb. Indeed:

ffmpeg -i ../utc_1800.mpg -vn -acodec amr_nb -ab 4 -y -ar 8000 x.3gp
ffmpeg version 0.4.9-pre1, build 4756, Copyright (c) 2000-2004 Fabrice
Bellard
configuration: --enable-mp3lame --disable-strip --enable-amr_nb
--enable-a52 --enable-gpl --enable-amr_wb --disable-shared
built on Jun 21 2005 11:33:44, gcc: 2.95.4 20011002 (Debian prerelease)
Input #0, mpeg, from '../utc_1800.mpg':
Duration: 00:00:57.0, start: 35802.163200, bitrate: 668 kb/s
Stream #0.0[0x1e0]: Video: mpeg1video, yuv420p, 352x288, 25.00 fps,
104857 kb/s
Stream #0.1[0x1c0]: Audio: mp2, 48000 Hz, mono, 32 kb/s
Output #0, 3gp, to 'x.3gp':
Stream #0.0: Audio: amr_nb, 8000 Hz, mono, 4 kb/s
Stream mapping:
Stream #0.1 -> #0.0
Press [q] to stop encoding
size= 50kB time=60.0 bitrate= 6.9kbits/s
video:0kB audio:38kB global headers:0kB muxing overhead 32.295381%

The resulting 3gp plays in realplayer on W2K so I could check the
size/quality tradeoff.

The problem is the license. Nothing on the source code site, but a quick
google found:

http://www.voiceage.com/amrsite/tech_nb_faqs.php

Which strongly hints *big* fees for any professional use...

So, any alternatives (on the lines of CELP, ACELP, LDCELP...)

[Michel Bardiaux]

Post by Michel Bardiaux

Post by Michel Bardiaux
The lowest possible bitrate I could achieve was GSM at 13kbits. Is
there some codec in lavc that can go below that? (Sample command would
be welcome). TIA.

ffmpeg -i ../utc_1800.mpg -vn -acodec amr_nb -ab 4 -y -ar 8000 x.3gp
ffmpeg version 0.4.9-pre1, build 4756, Copyright (c) 2000-2004 Fabrice
Bellard
configuration: --enable-mp3lame --disable-strip --enable-amr_nb
--enable-a52 --enable-gpl --enable-amr_wb --disable-shared
built on Jun 21 2005 11:33:44, gcc: 2.95.4 20011002 (Debian prerelease)
Duration: 00:00:57.0, start: 35802.163200, bitrate: 668 kb/s
Stream #0.0[0x1e0]: Video: mpeg1video, yuv420p, 352x288, 25.00 fps,
104857 kb/s
Stream #0.1[0x1c0]: Audio: mp2, 48000 Hz, mono, 32 kb/s
Stream #0.0: Audio: amr_nb, 8000 Hz, mono, 4 kb/s
Stream #0.1 -> #0.0
Press [q] to stop encoding
size= 50kB time=60.0 bitrate= 6.9kbits/s
video:0kB audio:38kB global headers:0kB muxing overhead 32.295381%

BTW how can I ascertain what is the bitrate in the audio stream alone
(ie without the 3gp wrapper)?

Post by Michel Bardiaux
The resulting 3gp plays in realplayer on W2K so I could check the
size/quality tradeoff.
The problem is the license. Nothing on the source code site, but a quick
http://www.voiceage.com/amrsite/tech_nb_faqs.php
Which strongly hints *big* fees for any professional use...
So, any alternatives (on the lines of CELP, ACELP, LDCELP...)

[Benjamin Larsson]

Post by Michel Bardiaux
[...]
The problem is the license. Nothing on the source code site, but a
http://www.voiceage.com/amrsite/tech_nb_faqs.php
Which strongly hints *big* fees for any professional use...
So, any alternatives (on the lines of CELP, ACELP, LDCELP...)

Speex (celp) , could be an alternative, it's free to use also.

MvH
Benjamin Larsson

[Michel Bardiaux]

Post by Benjamin Larsson

Post by Michel Bardiaux
[...]
The problem is the license. Nothing on the source code site, but a
http://www.voiceage.com/amrsite/tech_nb_faqs.php
Which strongly hints *big* fees for any professional use...
So, any alternatives (on the lines of CELP, ACELP, LDCELP...)

Speex (celp) , could be an alternative, it's free to use also.

Yes, I had a look, it sounds promising. Someone even proposed some time
ago to integrate speex in ffmpeg using external libs, his proposal was
not well received because of the xternal lib. But then, libgsm should
not have been accepted in cvs, and mp3lame should have been removed...

Post by Benjamin Larsson
MvH
Benjamin Larsson