From: batguano999
Sent: Wednesday, January 25, 2017 15:50
The next question is how to convert AVC3 to AVC1 or AAC. I have already
tried using ffmpeg and its aac codec. It was very slow and I still
couldn't
play the file. I have also tried the Nero encoder
This is pointless.
If you're converting from lossy to lossy aac you might as well convert from
lossy to lossy mp3.
What I had in mind was something like
mp4box -bs-switching no
to force AVC1. Also whether it is possible to force uniform sample rate to
minimise the size of the staz table.
By the way, what about this?
Create a 30 minute "raw aac" test file with FFmpeg...
ffmpeg -f lavfi -i sine=d=1800 -y 1800_testfile.aac
Mux it into m4a with mp4creator...
mp4creator -create=1800_testfile.aac 1800_testfile.m4a
See if it plays OK... with your "£19 AGPtEK player"
From: iz
Sent: Wednesday, January 25, 2017 14:30
One other long shot to try is to remove the MP4 container by remuxing to
plain old ADTS AAC. However, I'm guessing that even if that file played you
>may not be able to seek/ff/rw, so of limited use. You could also feed the
raw fragmented MP4 DASH file to your player, but I suspect that is even
less >likely to be >supported.
I had already tried playing the raw file in VLC. It played, but I noticed
seeking was slow. The file with the ADTS container did play in VLC, and
seeking seemed normal.
With -f lavfi I got
Requested output format 'lavfi' is not a suitable output format
tfr1800.aac: Invalid argument
(I had renamed the raw file from .m4a to .aac but I got the same message
when I renamed it back to .m4a) I used -f adts instead. The result was not
playable in the AGPtEK player.
I did not understand the -i parameter so I used -t for the duration.
These were the commands
ffmpeg -i tfr.aac -f adts -t 1800 -acodec copy tfr1800.aac
mp4creator -create tfr1800.aac tfr1800.m4a
Without -acodec copy it converted from aac to aac using ffmpeg's built in
codec, which was very slow. The resultant file with a duration of 1800s
(30min) did play on the AGPtEK player, but durations of 1900s and more did
not play. That is an improvement on 14min, but I noticed some drop outs not
in the FLAC conversion. I think I need to stick to FLAC or 320kbit/s MP3
for music and 128kbit/s MP3 for speech.
I still have a lot to learn about the relationship between containers and
content, and why a container can cause a problem for a player, or why AAC is
so much more difficult to decode than MP3 or FLAC. (The reason I commented
on price was that AAC players generally seem to be a lot more expensive than
MP3 players.) I have been struck by how astonishingly little non-BBC AAC
material is available for testing. There is a lot of free MP3 material. I
do not use iTunes.
Thank you both for your suggestions and comments.
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