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• reading video mpegts stream from stdin using libavformat libavcodec

  1er février 2012, par D Starkweather

  I'm trying to read video frames from stdin using ffmpeg's libav* lib collection. Simply passing "pipe:0" or "pipe :" as the filename to avformat_open_input_file() in my program does not do the trick. (e.g. cat /dev/video0 | ./myprogram OR ./myprogram < /dev/video0 ; it also fails using file.avi in place of /dev/video0).

  Peeking into ffmpeg.c, I find the following bit of code using tcsetattr() to set the termios :

  struct termios tty;
  
  
  
  if (tcgetattr (0, &tty) == 0) {
  
  oldtty = tty;
  
  restore_tty = 1;
  
  atexit(term_exit);
  
  
  
  tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP
  
                        |INLCR|IGNCR|ICRNL|IXON);
  
  tty.c_oflag |= OPOST;
  
  tty.c_lflag &= ~(ECHO|ECHONL|ICANON|IEXTEN);
  
  tty.c_cflag &= ~(CSIZE|PARENB);
  
  tty.c_cflag |= CS8;
  
  tty.c_cc[VMIN] = 1;
  
  tty.c_cc[VTIME] = 0;
  
  
  
  tcsetattr (0, TCSANOW, &tty);
  
  }
  
  signal(SIGQUIT, sigterm_handler); /* Quit (POSIX).  */
  
  }
  
  
  
  avformat_network_deinit();
  
  
  
  signal(SIGINT , sigterm_handler); /* Interrupt (ANSI).    */
  
  signal(SIGTERM, sigterm_handler); /* Termination (ANSI).  */
  
  signal(SIGXCPU, sigterm_handler);

  However, when I try this, it appears to have no effect. What settings do I need in the termios struct to continuously read video frames in ?

  Currently, all i am able to do is call av_read_frames a few times (return code 0) before it usually either segfaults or hangs waiting. The buffer usually contains just a blank screen (all black). With any luck, the video buffer will contain the first video frame it comes across, but does not update to the later frames.

  (I'm running this on Debian 6.0) Here's my version of ffmpeg :

  ffmpeg version N-36936-g4cf81d9 Copyright (c) 2000-2012 the FFmpeg
  developers built on Jan 19 2012 20:51:47 with gcc 4.4.5
  configuration : —enable-shared —enable-gray —enable-hardcoded-tables
  —enable-runtime-cpudetect —enable-libmp3lame —enable-libopenjpeg —enable-librtmp —enable-libtheora —enable-libvorbis —enable-libx264 —enable-libxvid —enable-zlib —enable-gpl libavutil 51. 34.101 / 51. 34.101 libavcodec 53. 57.100 /
  53. 57.100 libavformat 53. 30.100 / 53. 30.100 libavdevice 53. 4.100 / 53. 4.100 libavfilter 2. 59.101 / 2. 59.101 libswscale 2. 1.100 / 2. 1.100 libswresample 0. 6.100 /
  0. 6.100 libpostproc 52. 0.100 / 52. 0.100 Hyper fast Audio and Video encoder usage : ffmpeg [options] [[infile options] -i
  infile].

  Thank you very much for any help helpful tips. It is much appreciated.

  D. Grant Starkweather

• FFMPEG - Correct command line parameters to create a H.264 Streaming MP4 from a set of images

  5 janvier 2012, par Adam

  I have no problems viewing a video created by my current parameters in a HTML5 browser, Flash player, Windows Phone 7, Android Phone, etc. However, they won't display on iPhone or iPad. If I modify the video using Super and select "Enable Streaming" checkbox they work on iPhone and iPad suddenly. We are suspecting that my command line parameters are incorrect for enabling h.264 streaming and are instead generating a "progressive download" video.

  I'm pretty new to FFMPEG and don't understand a lot of the parameters. Can anyone help correct my existing parameters, or maybe provide the missing parameters, etc ?

  Thanks in advance.

  My current FFMPEG command line paramters are :

  ffmpeg.exe 
   -r 30 
   -threads 4 
   -f image2 
   -i .\frame%05d.jpg 
   -i audioFile  
   -acodec aac 
   -ab 128k 
   -ar 44100
   -vcodec h264 
   -crf 27 
   -coder 1 
   -flags +loop 
   -cmp +chroma 
   -partitions +parti4x4+partp8x8+partb8x8 
   -me hex 
   -subq 5 
   -me_range 16 
   -g 60 
   -keyint_min 25 
   -sc_threshold 40 
   -i_qfactor 0.71 
   -b_strategy 1 
   out.mp4
  

• Fun With Tablets And Amazon’s App Store

  24 décembre 2011, par Multimedia Mike — General, amazon, android, app store, cyanogenmod, ios, smurfs, tablet

  I bought an Android tablet a few months ago. It is less expensive than the best tablets but no where near the bottom end of the market. I think it’s pretty good. However, one downside is that it’s not “certified” to use Google’s official marketplace. That would seem to be somewhat limiting, however…

  Enter Amazon’s Android App Store
  Amazon got into the business of selling Android Apps some time ago. I started experimenting with this on a Nexus One phone that Google gave me. When I installed the App Store on the Android tablet and logged in, I was pleasantly surprised to see all of my Amazon apps ready for downloading onto the tablet.

  So I have an App Store for use with this Android tablet.

  Anyway, the reason I bring this up is because I managed to screw up this tablet in an unusual and humorous manner. You might be wondering if an app downloaded from the Amazon App Store requires the App Store to be present in order to run. The answer is : Oh yeah ! It works like this :

  
  
  

  This means that if — perhaps out of curiosity, for example — you login to the Amazon App Store, download an app, install it, and then subsequently log out of the App Store or uninstall it altogether, the downloaded app will decline to run until you log back into the store.

  Here’s the thing– I wanted to provide a minimal level of security for my Android tablet. At the very least, I wished to lock the Amazon App Store itself since Amazon is famously (and, let’s face it, understandably) reluctant to deliberately add any friction to their shopping processes. I.e., without any external protection app, the App Store app would allow anyone to purchase any app using my tablet.

  So I purchased App Protector Pro from the Amazon App Store and it worked quite well. By default, it also password protects against modifying any system settings as well as installing new apps.

  So, here’s where I screwed up : App Protector Pro was doing its faithful duty and I uninstalled the Amazon App Store as an experiment. Suddenly, no apps obtained from the App Store would work unless I reinstalled the App Store. Okay, fair enough, except for one thing– App Protector Pro wouldn’t run without the App Store. Well, it did, it started to, tried to, but then exited. So I couldn’t re-install the App Store :

  
  
  Oops
  

  I eventually learned how to perform a factory reset of the unit which solved the problem. And, as indicated earlier, all of my apps were available for me to re-download.

  Modding, Cyanogen-style
  Open source aficionados will likely point out that there are alternate firmware options which allow me to take control of my Android tablet in a free and open manner. Among these options is CyanogenMod. After I got stuck in the situation described above, I thought I would have to resort to such an option.

  On the plus side, researching alternative firmware options is what taught me to boot the device into a recovery mode and ultimately restore to a factory default setting. But if you’ll allow me to indulge in a mini-rant regarding accessibility of open source software : I was more than a little frustrated in trying to understand what CyanogenMod could possibly offer me. Their homepage says it’s “an aftermarket firmware”. I’m not entirely sure what that means or how it can benefit me. Fortunately, they have a full feature list linked from the front page. They are, in order : Lockscreen gestures, phone goggles, OpenVPN, incognito mode, themes support, and DSP equalizer. I can’t say that any of those really add any value for me. I’d love to know if CyanogenMod supports Google Android Market and various other Google apps (such as maps and GMail). That’s a question that I can’t seem to find the answer to.

  The themes feature opens another old wound for me. Back around 1999 when I was first getting into Linux in a serious way, I remember that themes were a big theme at the Linux User Groups I would attend. I also remember lots are online articles at the time that emphasized how highly customizable the Linux desktop was in comparison to Windows 9x. I was bothered for 2 reasons : First, I thought there were more pressing problems that needed to be addressed in Linux ; and second, none of these customization options seemed particularly straightforward ; many apparently required hours of compiling and tinkering.

  Small digression. Anyway, back to CyanogenMod, I was glad to see that they prominently display a button in order to “View Video Tour”. Ah, internet video has us so spoiled these days. I was eager to see this aftermarket firmware in action to see what it could do for me. However, the link leads to… a forum post ? The thread seems to discuss how it would be a cool idea if the community could put together a video tour. At this point, the investigation just seems bizarre. It feels like a bunch of kids doing their best to do things the grown-up way.

  Okay, sorry, rant over. I try to stay positive these days. I’m sure the CyanogenMod folks are doing great, fun, and interesting work on their project. The problems they choose to solve might lack mainstream appeal, however.

  Free iPad
  Ultimately, I recently unloaded the little Android tablet because, well… when a free iPad comes your way, lower spec tablets feel a little silly to keep around. Yeah, it’s great to play around with. Though here’s one unsettling thing I noticed about Apple’s App Store. While browsing for worthwhile games to indulge in, I noticed that they had a section for “Top Grossing Games”. This was a separate list from the “Top Apps” charts. I found the list weird for 2 reasons : 1) Why do I care which games are raking in the most cash ? How does this communicate value to me, personally ? Seriously, why would I base a purchasing decision around which vendor has earned the most money ?

  Anyway, let’s move on to reason #2 this was scary : Most of the games in this list had a price of FREE. One of them was that Capcom Smurfs game that stirred up controversy some months ago because of kids making unsupervised in-app purchases of virtual smurfberries. I tend to think that a top-grossing, free to play game is probably one that heavily encourages in-app purchases. Strange how this emerging trend actually encourages me to seek out games from the “top paid” list vs. “top free”.