[FFmpeg-trac] #2686(avcodec:open): Native AAC encoder collapses at high bitrates on some samples
FFmpeg
trac at avcodec.org
Sun May 4 09:47:16 CEST 2014
#2686: Native AAC encoder collapses at high bitrates on some samples
-------------------------------------+-------------------------------------
Reporter: Kamedo2 | Owner:
Type: defect | Status: open
Priority: normal | Component: avcodec
Version: git-master | Resolution:
Keywords: aac | Blocked By:
regression | Reproduced by developer: 1
Blocking: |
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
Comment (by Kamedo2):
A Result of a quick analysis, using 17 music tracks:
'''Default ABR''' 128kbps
Min / '''Average''' / Max bitrate: 129 / '''130''' / 131 kbps
Average Speed: '''12.9'''x
ffmpeg_r62950_v8f -i %i -c:a aac -strict experimental -b:a 128k %o
This sounds great for 128 kbps.
'''Default VBR''' q1
Min / '''Average''' / Max bitrate: 169 / '''192''' / 211 kbps
Average Speed: '''14.1'''x
ffmpeg_r62950_v8f -i %i -c:a aac -strict experimental -q:a 1 %o
Sounds very clear, but not something expected from 192 kbps.
'''ABR -cutoff 22000'''
Min / '''Average''' / Max bitrate: 3 / '''4''' / 4 kbps
Average Speed: '''14.1'''x
ffmpeg_r62950_v8f -i %i -c:a aac -strict experimental -b:a 64 -cutoff
22000 %o
The sound is almost silent. The value very close to nyquist freq seems to
cripple the LPF.
'''ABR with ms_off'''
Min / '''Average''' / Max bitrate: 128 / '''129''' / 131 kbps
Average Speed: '''14.1'''x
ffmpeg_r62950_v8f -i %i -c:a aac -strict experimental -b:a 128k -aac_coder
anmr %o
Sounds bad when transients exist.
'''ABR with -aac_coder fast'''
Min / '''Average''' / Max bitrate: 128 / '''134''' / 141 kbps
Average Speed: '''28.0'''x
ffmpeg_r62950_v8f -i %i -c:a aac -strict experimental -b:a 128k -aac_coder
fast %o
This is fast, but with very bad quality. I don't know if there's good use
of this option.
'''ABR with -aac_coder anmr'''
Min / '''Average''' / Max bitrate: 130 / '''134''' / 141 kbps
Average Speed: '''8.0'''x
ffmpeg_r62950_v8f -i %i -c:a aac -strict experimental -b:a 128k -aac_coder
anmr %o
Sounds bad when transients exist. Noticably worse than the default ABR,
and it's slow.
'''VBR with -aac_coder anmr'''
Min / '''Average''' / Max bitrate: 172 / '''191''' / 213 kbps
Average Speed: '''7.5'''x
ffmpeg_r62950_v8f -i %i -c:a aac -strict experimental -q:a 1 -aac_coder
anmr %o
Sounds slightly bad when transients exist. It's slow.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/2686#comment:281>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
More information about the FFmpeg-trac
mailing list