If you're using FFmpeg SVN and you experience a crash or odd behavior, then you may be interested in submitting a bug report to the FFmpeg project. If you are using FFmpeg from the Ubuntu repository, please report bugs to Launchpad instead.
Read the bug report guidelines
Reporting a Bug To The FFmpeg Project. You don't want to get flamed for not strictly following directions. The goal of this post is not to duplicate the guidelines, but to provide some more instruction that may be useful to Ubuntu users, to help make reporting a bug less intimidating, and to make your bug report more informative.
It is a good idea to ask the #ffmpeg IRC channel or ffmpeg-user mailing list if anyone else can duplicate your bug. Insight from others may reveal your issue as not a bug or they can help provide additional information.
Search for your bug
Go to the FFmpeg Issue Tracker (yes, it's horrendously slow), and then perform a search before creating a new bug report. Someone else may have already reported your bug. You don't want to get flamed for making a duplicate bug report. There are many search options. I generally just use the All text* search box and leave everything else as is.
Report your bug
If you find nothing, then register and then create your new bug report.
Creating a FFmpeg Bug Report
Title: Give a detailed and useful title. A title like segmentation fault when capturing screen with x11grab is better than ffmpeg crashes.You can generally ignore the rest of the options.
Type: Choose bug.
Priority: Choose important for crashes/segmentation faults and normal for everything else.
Status: I've always used New / New when creating a bug.
Nosy List: Adding your user name to the Nosy List will e-mail you when someone replies to your bug or updates the bug priority.
Change Note: This is where you provide a description of the bug, how to duplicate the bug, and where samples are located.
Change Note Continued...
Always provide the most simple ffmpeg command. For example, if you experience a crash with:
...you should also try a more basic command:
ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 30 -s 1024x768 -i :0.0 -acodec pcm_s16le \
-vcodec libx264 -vpre lossless_ultrafast -threads 0 output.mkv
If the simple command still crashes use it instead so the developers can rule out extra junk that may cause issues such as threads or external encoders.
ffmpeg -f x11grab -r 30 -s 1024x768 -i :0.0 output.mpg
Now submit your bug report. It will be assigned an issue ID number, such as issue1392, which will be important if you want to submit a sample file.
Providing a sample
You should provide a sample if it is important to reproducing the bug or if a developer asks for one. This is explained in the Submitting Sample Media section of Reporting a Bug To The FFmpeg Project. All that I will add is when creating a new directory as the page instructs, name it the same as your issue number. This will make life easier for the server admins. Then navigate back to your bug report and make a comment indicating where your sample is. Something like: "Sample located at incoming/issue1392/descriptive_sample_name.foo".
gdb output and backtrace
A developer will most likely ask you to provide the gdb output and a backtrace if you are reporting a crash bug. This is mostly described at Reporting a Bug To The FFmpeg Project. Some additional info:
Install gdb if you don't have it:
ffmpeg_g is located in your ~/ffmpeg directory if you followed HOWTO: Install and use the latest FFmpeg and x264.
sudo apt-get install gdb
If you need additional help, the best places to ask questions are the #ffmpeg IRC channel, the ffmpeg-user mailing list, or you can reply to this post.