Thank you .. I will use this episode to add some effect to my website.

Inkscape is lucky! Because there is a screencaster lik you ;).

Yup, I know exactly what you mean. I hear the hum too. Unfortunately I had broken my Logitech USB mic that I used on my WinXP machine. Had to use my old pedistal mic (euphemism for super shitty microphone) which picks up a lot of noise. Since the original sound was quiet I had to increase the sound level by nearly 200% for this episode. So basically, I had to play some games with the audio. It’s possible that I could have toned that down a little in audacity. I had another Logitech USB mic but I didn’t have it in my procession at the time of the recording. Can’t say it won’t happen again but at least I know what causes it.

Maybe I can get Richard to help adjust the sound and re-upload it to the site. Matter of fact, let us work on it. When it’s done I’ll post back here.

Per chance was this screencst done in WinXP. I’m getting a horrible background hum throughout this, and only this, screencast. I too, would prefer a slightly blurry video than a humming noise, if that’s the case. Thanks for your screencasts.

Cheers

Thanks for the tip on “-mc 0″. Luckily it’s not part of the mp4 scripts that we settle on. Serge figured out what it took to make them work in the end. I really appreciated his help.

If and when Richard and I are ready to go mp4 maybe I can bother you with another round of questions. Your input was important to me in the past. Maybe I can get Serge to jump in too. Even though Richard and I have been producing screencasts for a while now, we still could use some education in regard to video encoding.

Where was I? You started at the end of 2006 which by very coincidence is the time when I launched my site and had my fair share of Encoding Hell. Very probably I would not have been much of help at that time. Bit by bit I acquired some knowledge of codecs and formats since then. A lot of time I have spent by experimenting with the endless amount of options. But in the end it has earned me a couple of beers, so I can’t complain.

I’m thinking if I just hold out long enough you’ll make Inkscape tutorials too.

Yes, I am fully aware of the 800×600, divisible by 16 thing. We had a perfect reason for choosing that resolution when we first started. I forget now. Actually, I would like to go bigger and not smaller. This was something that I was going to tackle when Inkscape 0.46 was officially released. The application dimensions will change so I will be forced to do something about it. It’s important for us to stay absolutely consistent no matter the video scale that we choose. If compression suffers a little then it’s just a minor thing. It’s very important then when you screencast that your application window (Inkscape) is identical or close to the dimensions or resolution of your final video. So for instance, if our Inkscape window size is 800×600 and we output to 800×600 video then the video will be crisp. You’ll notice that some of my opensuse/Inkscape screencast are sometimes a little blurry. That is because I cannot get an 800×600 application window. I get something more like 865×649 in KDE 3.5.7. In WinXP I can get an Inkscape window of 800×600 and that’s why my final video looks so sharp. There is no scaling needed on my WinXp machine. (I would rather screencast in Linux because I get better sound than I do in Windows)

Great set of comments here. This has been pretty valuable information. I really appreciate your efforts, Serge. I definitely owe you a beer or two. By the way, where th hell were you when we first started?

Cheers

mencoder part1.mp4 part2.mp4 -o part1_2.mp4 -of lavf -lavfopts format=mp4 -oac lavc -ovc lavc -lavcopts acodec=libfaac:vcodec=libx264:vmax_b_frames=0:aglobal=1:vglobal=1 -vf harddup

No problem, even the Flash media player played the resulting MP4 fine in the browser window. But I would avoid a lot of transcoding. It will hurt quality. Maybe it is better to use the original files (AVI, Theora) and concatenate those at once in the final MP4 video.

And now for something completely different. I just now noticed that the size of the video is 800×600. For optimal compression dimensions which are a multiple of 16, are to be preferred. In this case 768×576 for example which has the same aspect ratio as 800×600. It is not a big deal but will help to reduce size and avoid compression artefacts.

I wasn’t really happy about that 21 fps switch either. Seemed like a half-assed way to go about it. Just supplying the -vf harddup switch is the answer. I swear I tried that last night but maybe I didn’t.

Nevertheless, I think you have it all figured out for me. I’ll run your script back on a few other episodes and check for errors.

This gives me a good foundation to work with. I’m not sure if it makes sense to continue encoding in the avi format and then convert to mp4 or just go straight to mp4. It’s easier to work with the avi’s in terms of adding our intro and Richard’s “speedcasts”. Joining mp4’s is still a mystery to me.

I think what I’ll do is offer up some mp4 samples for our viewers to download. Best way I know to find out how the video plays on all kinds of computers.

mencoder input.avi -o output.mp4 -of lavf -lavfopts format=mp4 -oac lavc -ovc lavc -lavcopts acodec=libfaac:vcodec=libx264:vmax_b_frames=0:aglobal=1:vglobal=1

Indeed, audio and video were out of sync due to lots of duplicate frames. Then I added -vf harddup and the video worked fine (!) both in MPlayer, Totem with Gstreamer backend and FlowPlayer (a Flash media player) in the browser window. Adding -mc 0 or -ofps 21 did not make a difference: the video stayed in sync.

Unfortunately is VLC on my system broken. There are issues with the latest FFmpeg and those will not be resolved until version 0.9 of VLC. That is really a pity now. Audio works however, and I noticed in View -> Stream and Media Info that VLC thinks that the audio bit rate is 705 kb/s which is way to high. When I use the original AVI file, it shows the correct 128 kb/s. Adding abitrate=128 to -lavcopts or something like -af channels=1 did not help. VLC shows also that the AAC audio file has the SBR extension but as far as I know that should not be a problem.

What can I say? I am puzzled by -ofps 21. How did you find this out by the way? It does not make any sense to me and I think we are looking at an artefact. Is it needed only for VLC or also for smplayer and Quicktime? Are there differences in the messages that VLC shows in View -> Messages depending on whether -ofps is or is not used? Does aglobal=3 and vglobal=3 help?

Conclusion: it seems safe to say that your script works although I am not totally comfortable with that -ofps 21. I wonder what happens if you use the original Theora files of recordmydesktop.

We have entered Encoding Hell after all

You probably won’t believe this but I got your script working by using this combination:

mencoder input.avi -o output.mp4 -of lavf -lavfopts format=mp4 -oac lavc -ovc lavc -lavcopts acodec=libfaac:vcodec=libx264:vmax_b_frames=0:aglobal=1:vglobal=1 -vf harddup -mc 0 -ofps 21

Did you notice that 21 fps? Odd isn’t it? I can control the a/v sync by changing this frame rate. Too high of a frame rate (25 or 30) and the video speeds up. Too low of a frame rate (15, 20) and the video slows down like slow motion. 21 fps seems to be the sweet spot.

I converted episode ep034-1.avi to mp4 with the above script and it plays great in smplayer and vlc. If you get a chance to, maybe you can download the same episode and run the above script back to convert it. Hopefully you can let me know how it plays for you. This might be the answer to how Richard and I could convert our avi’s to mp4’s in the future.

Thanks for the script, Serge.

I use smplayer and vlc usually when I watch video.I’m trying all kinds of things with mencoder. I’ll try some of your option switches and see what I get.

I checked with a chunk of 5 minutes (XviD and MP3 in AVI container so different than the format of your screen recording) on my system and I did not experience sync issues in the final MP4 film. Is the video slowly getting more and more out of sync or is there an initial delay/advance which is constant during the rest of the film? Which media player has problems or do they all show sync problems?

Options which could help: -vf harddup, -mc 0, -ofps , -noskip

Yes, I still get syncing issues. I think the audio is on cue…it’s the video that plays slightly faster. I didn’t notice any output errors in my terminal after the encode either. Of course I might have been distracted by my daughter cart-wheeling all last night…Daddy? Whatch this…Daddy? Watch this…Daddy? Watch this…:)

Serge, your script works on my opensuse box. Although, the video plays a little faster than normal and I don’t get any sound. Interesting anyway.

MPlayer dev-SVN-r24712-4.2.1

Just realized my mistake:
Scratch the above. Ok, I think I’m too tired to concentrate. Sound does work except that it’s out of sync with the video. Apparently I had audacity running and that was interfering with the sound earlier. Dumb ass attack on my part…sorry.

I’ll see if I can upgrade mplayer on my ubuntu 7.10 box.

i_certify_that_my_video_stream_does_not_use_b_frames

I am not joking, Serge