Sunday, November 23, 2008

minor problems from new Fedora 9

I'm glad I took the time to rerun my main encoding script, as it showed a number of errors due to changes between Fedora 7 and Fedora 9. The first four I've encountered are specific to VLC; the last couple are problems with the latest FFMPEG install.

VLC Problems
1) permissions issue
This is not necessarily a problem with a change in Fedora, just a problem with how I've reorganized some of my videos to be owned by a different user. When I ran VLC to convert one of the files, I got this error:
[00000436] access_output_file access out error: cannot open `20081123.m2t' (Permission denied)
[00000434] stream_out_standard stream out error: no suitable sout access module for `file/ts://20081123.m2t'

At least the text of the error was not ambiguous..Permission Denied! :) Once I identified the permissions problem and granted appropriate privileges to the file, this message went away. A good option when running VLC is to run it with the -vvv verbose switch in order to get full debug stream on what is going on.

2) command line VLC doesn't accept quit anymore
VLC used to quit properly when my old script used to look like this:
vlc --sout '#duplicate{dst=std{access=file,mux=ts,dst="output.m2t"}}' vlc:quit

VLC's authors must now be enforcing command line syntax, as there now needs to be two slashes after the colon in the quit directive. So the following works again:
vlc --sout '#duplicate{dst=std{access=file,mux=ts,dst="output.m2t"}}' vlc://quit

Update 12/13/2008
3) Can't run VLC as root anymore
When I tried to run VLC from a script as root, I got this error:
VLC is not supposed to be run as root. Sorry.
If you need to use real-time priorities and/or privileged TCP ports
you can use vlc-wrapper (make sure it is Set-UID root first and
cannot be run by non-trusted users first).

For security reasons, it is probably better that VLC enforces this. I addressed the issue in two ways:
1) login as a non-privileged user to run VLC
2) if I need to run VLC as root, I will use the "su" command to run the command using a different user's privileges. Using my non-privileged "mule" user, the syntax of the command is something like the below. I am using command line VLC, which is started by "cvlc":
su mule -c "cvlc --sout '#duplicate{dst=std{access=file,mux=ts,dst=output.mp4}}' vlc://quit"

In either case, I made sure that all my files are owned by or at least accessible by the user that runs VLC.
end update

4) Some obscure dbus error
[00000415] inhibit interface error: Failed to connect to the D-Bus session daemon: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.

Looking up this error in Google points to a number of threads regarding the reinstall of dbus message bus. However, this error doesn't inhibit my ability to convert video, so I'm not going to do anything about this error right now.

5) a bunch of other GUI related errors
[00000415] main interface error: no suitable interface module [00000001] main libvlc error: interface "inhibit,none" initialization failed
[00000001] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
No protocol specified
[00000421] qt4 interface error: Could not connect to X server
No protocol specified
[00000421] skins2 interface error: Cannot open display
[00000421] skins2 interface error: cannot initialize OSFactory

Even with these errors, VLC does start, though in remote control mode only. You can quit out of this mode by typing "quit" after the line that reads:
Remote control interface initialized. Type `help' for help.

Since I am running VLC as part of a command script, I changed the script to use the command-line version of VLC, CVLC as below:
cvlc --sout '#duplicate{dst=std{access=file,mux=ts,dst="output.m2t"}}' vlc://quit

Note that the quit directive is still "vlc://quit". Eventually, I do want to run VLC's GUI mode, so I will have to return to fixing this error.

FFMPEG Problems: library naming
Running this FFMPEG command on my shiny new Fedora 9 system:
ffmpeg -i input.mpg -threads 8 -f mov -vcodec mpeg4 -qscale 3 -s 320x180 -r 29.97 -aspect 16:9 -acodec aac -ac 2 -ar 48000 -ab 448k

Gave me this error:
Unknown encoder 'aac'

Researching on Google led me to this thread, which stated that the proper syntax is to now using the name of the library, libfaac:

The version of FFMPEG that I had been using with Fedora 7 was SVN version 9975. With Fedora 9, that is revised to SVN version 12135. During the interim between the two versions, command syntax now requires full library names.

So using the proper library name 'libfaac' fixed the issue and allowed ffmpeg to continue:
ffmpeg -i input.mpg -threads 8 -f mov -vcodec mpeg4 -qscale 3 -s 320x180 -r 29.97 -aspect 16:9 -acodec libfaac -ac 2 -ar 48000 -ab 448k

The same error occurred with my command to encode a file to h264 format:
ffmpeg -y -i input.mpg -v 1 -threads 8 -vcodec h264 -b 250k -bt 175k -refs 1 -loop 1 -deblockalpha 0 -deblockbeta 0 -parti4x4 1 -partp8x8 1 -me full -subq 6 -me_range 21 -chroma 1 -slice 2 -bf 0 -level 30 -g 300 -keyint_min 30 -sc_threshold 40 -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.7 -qmax 51 -qdiff 4 -i_qfactor 0.71428572 -maxrate 450k -bufsize 2M -cmp 1 -s 720x480 -acodec libfaac -ab 160k -ar 48000 -ac 2 -f mp4 -pass 2 -threads 8 output.mp4

I received this error:
Unknown encoder 'h264'

The solution was to simply replace 'h264' with 'libx264' in the command line:

the mule

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