Since I switched from version 1.0.3 to 1.0.5 I experienced bad AAC output quality when using acodec=mp4a with whatever bitrate or samplerate.
The same problem exits for the new 1.1.0-pre4 version.
I have prepared a batch script to produce some sample m4a files:
Code: Select all
vlc-1.0.3\vlc.exe -vvv bach.mp3 :sout="#transcode{acodec=mp4a,ab=128,channels=2,samplerate=44100}:std{access=file,mux=mp4,dst=vlc-1.0.3_aac_test_bach.m4a}" :no-prefer-system-codecs vlc://quit
vlc-1.0.5\vlc.exe -vvv bach.mp3 :sout="#transcode{acodec=mp4a,ab=128,channels=2,samplerate=44100}:std{access=file,mux=mp4,dst=vlc-1.0.5_aac_test_bach.m4a}" :no-prefer-system-codecs vlc://quit
vlc-1.1.0-pre4\vlc.exe -vvv bach.mp3 :sout="#transcode{acodec=mp4a,ab=128,channels=2,samplerate=44100}:std{access=file,mux=mp4,dst=vlc-1.1.0-pre4_aac_test_bach.m4a}" :no-prefer-system-codecs vlc://quit
In 1.0.5 and 1.1.0-pre4, however, the files are different each time.
Conversion speed in 1.0.3 is about 4 sec for the 60 sec mp3 input file.
For 1.0.5 it is 6 sec, and for 1.1.0-pre4 about the same.
I'm not sure what happened to the codec after version 1.0.3.
However, if I replace the libavcodec_plugin.dll of 1.0.5 by that from 1.0.3 I get good quality AAC.
Another workaround:
When setting channels=1 the artefacts in 1.0.5 and 1.1.0-pre4 seem to disappear and the files are identical each time.
I also tried setting aenc=ffmpeg{aac-profile=low} explicitly but that didn't help.
I wish this could be fixed in 1.1.0 because AAC is important when encoding for mobile devices, escpecially in videos.
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Sample output
vlc-1.0.3_aac_test_bach.m4a
vlc-1.0.5_aac_test_bach.m4a
vlc-1.1.0-pre4_aac_test_bach.m4a
