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• Elacarte Presto Tablets

  14 mars 2013, par Multimedia Mike — General

  I visited an Applebee’s restaurant this past weekend. The first thing I spied was a family at a table with what looked like a 7-inch tablet. It’s not an uncommon sight. However, as I moved through the restaurant, I noticed that every single table was equipped with such a tablet. It looked like this :

  
  
  

  For a computer nerd like me, you could probably guess that I was be far more interested in this gadget than the cuisine. The thing said “Presto” on the front and “Elacarte” on the back. Putting this together, we get the website of Elacarte, the purveyors of this restaurant tablet technology. Months after the iPad was released on 2010, I remember stories about high-end restaurants showing their wine list via iPads. This tablet goes well beyond that.

  How was it ? Well, confusing, mostly. The hostess told us we could order through the tablet or through her. Since we already knew what we wanted, she just manually took our order and presumably entered it into the system. So, right away, the question is : Do we order through a human or through a computer ? Or a combination ? Do we have to use the tablet if we don’t want to ?

  Hardware
  When picking up the tablet, it’s hard not to notice that it is very heavy. At first, I suspected that it was deliberately weighted down as some minor attempt at an anti-theft measure. But then I remembered what I know about power budgets of phones and tablets– powering the screen accounts for much of the battery usage. I realized that this device needs to drive the screen for about 14 continuous hours each day. I.e., the weight must come from a massive battery.

  The screen is good. It’s a capacitive touchscreen, so nice and responsive. When I first spied the device, I felt certain it would be a resistive touchscreen (which is more accurately called a touch-and-press-down screen). There is an AC adapter on the side of the tablet. This is the only interface to the device :

  
  
  

  That looks to me like an internal SATA connector (different from an eSATA connector). Foolishly, I didn’t have a SATA cable on me so I couldn’t verify.

  User Interface
  The interface options are : Order, Games, Neighborhood, and Pay. One big benefit of accessing the menu through the Order option is that each menu item can have a picture. For people who order more by picture than text description, this is useful. Rather, it would be, if more items had pictures. I’m not sure there were more pictures than seen in the print menu.
  
  For Games, there were a variety of party games. The interface clearly stated that we got to play 2 free games. This implied to me that further games cost money. We tried one game briefly and the food came.

  2 more options : Neighborhood– I know I dug into this option, but I forget what it was. Maybe it discussed local attractions. Finally, Pay. This thing has an integrated credit card reader. There is no integrated printer, though, so if you want one, you will have to request one from a human.

  Experience
  So we ordered through a human since we didn’t feel like being thrust into this new paradigm when we just wanted lunch. The staff was obviously amenable to that. However, I got a chance to ask them a lot of questions about the particulars. Apparently, they have had this system for about 5 months. It was confirmed that the tablets do, in fact, have gargantuan batteries that have to last through the restaurant’s entire business hours. Do they need to be charged every night ? Yes, they do. But how ? The staff described this several large charging blocks with many cables sprouting out. Reportedly, some units still don’t make it through the entire day.

  When it was time to pay, I pressed the Pay button on the interface. The bill I saw had nothing in common with what we ordered (actually, it was cheaper, so perhaps I should have just accepted it). But I pointed it out to a human and they said that this happens sometimes. So they manually printed my bill. There was a dollar charge for the game that was supposed to be free. I pointed this out and they removed it. It’s minor, I know, but it’s still worth trying to work out these bugs.

  One of the staff also described how a restaurant doesn’t need to employ as many people thanks to the tablet. She gave a nervous, awkward, self-conscious laugh when she said this. All I could think of was this Dilbert comic strip in which the boss realizes that his smartphone could perform certain key functions previously handled by his assistant.

  Not A New Idea
  Some people might think this is a totally new concept. It’s not. I was immediately reminded of my university days in Boulder, Colorado, USA, circa 1997. The local Taco Bell and Arby’s restaurants both had touchscreen ordering kiosks. Step up, interact with the (probably resistive) touchscreen, get a number, and step to the counter to change money, get your food, and probably clarify your order because there is only so much that can be handled through a touchscreen.

  What I also remember is when they tore out those ordering kiosks, also circa 1997. I don’t know the exact reason. Maybe people didn’t like them. Maybe there were maintenance costs that made them not worth the hassle.

  Then there are the widespread self-checkout lanes in grocery stores. Personally, I like those, though I know many don’t. However, this restaurant tablet thing hasn’t won me over yet. What’s the difference ? Perhaps that automated lanes at grocery stores require zero external assistance– at least, if you do everything correctly. Personally, I work well with these lanes because I can pretty much guess the constraints of the system and I am careful not to confuse the computer in any way. Until they deploy serving droids, or at least food conveyors, there still needs to be some human interaction and I think the division between the human and computer roles is unintuitive in the restaurant case.

  I don’t really care to return to the same restaurant. I’ll likely avoid any other restaurant that has these tablets. For some reason, I think I’m probably supposed to be the ideal consumer of this concept. But the idea will probably perform all right anyway. Elacarte’s website has plenty of graphs demonstrating that deploying these tablets is extremely profitable.

• Statically built FFMPEG binary segmentation fault

  12 février 2020, par stevendesu

  I want to create a custom build of FFMPEG which rips out everything except for the ability to transmux HLS videos to MP4, and I need this build to be 100% static with no external dependencies

  I tried using the following configuration :

  ./configure \
  
      --extra-cflags='-static -static-libstdc++ -static-libgcc' \
  
      --extra-cxxflags='-static -static-libstdc++ -static-libgcc' \
  
      --extra-ldflags='-static -static-libstdc++ -static-libgcc' \
  
      --pkg-config-flags='--static' \
  
      --enable-static \
  
      --disable-shared \
  
      --disable-runtime-cpudetect \
  
      --disable-autodetect \
  
      --disable-ffplay \
  
      --disable-ffprobe \
  
      --disable-doc \
  
      --disable-avdevice \
  
      --disable-swresample \
  
      --disable-swscale \
  
      --disable-postproc \
  
      --disable-pthreads \
  
      --disable-w32threads \
  
      --disable-os2threads \
  
      --enable-network \
  
      --disable-dct \
  
      --disable-dwt \
  
      --disable-error-resilience \
  
      --disable-lsp \
  
      --disable-lzo \
  
      --disable-mdct \
  
      --disable-rdft \
  
      --disable-fft \
  
      --disable-faan \
  
      --disable-pixelutils \
  
      --disable-encoders \
  
      --disable-decoders \
  
      --disable-hwaccels \
  
      --disable-muxers \
  
      --enable-muxer=mov \
  
      --enable-muxer=mp4 \
  
      --disable-demuxers \
  
      --enable-demuxer=hls \
  
      --enable-demuxer=mpegts \
  
      --enable-demuxer=h264 \
  
      --enable-demuxer=aac \
  
      --disable-parsers \
  
      --enable-parser=h264 \
  
      --enable-parser=aac \
  
      --disable-bsfs \
  
      --disable-protocols \
  
      --enable-protocol=tcp \
  
      --enable-protocol=tls \
  
      --enable-protocol=http \
  
      --enable-protocol=https \
  
      --enable-protocol=hls \
  
      --disable-indevs \
  
      --disable-outdevs \
  
      --disable-devices \
  
      --disable-filters \
  
      --disable-alsa \
  
      --disable-appkit \
  
      --disable-avfoundation \
  
      --disable-bzlib \
  
      --disable-coreimage \
  
      --disable-iconv \
  
      --disable-lzma \
  
      --enable-openssl \
  
      --disable-sndio \
  
      --disable-sdl2 \
  
      --disable-securetransport \
  
      --disable-xlib \
  
      --disable-zlib \
  
      --disable-amf \
  
      --disable-audiotoolbox \
  
      --disable-cuda-llvm \
  
      --disable-cuvid \
  
      --disable-d3d11va \
  
      --disable-dxva2 \
  
      --disable-ffnvcodec \
  
      --disable-nvdec \
  
      --disable-nvenc \
  
      --disable-v4l2-m2m \
  
      --disable-vaapi \
  
      --disable-vdpau \
  
      --disable-videotoolbox \
  
      --disable-debug

  This looked about like what I wanted :

  install prefix            /usr/local
  
  source path               .
  
  C compiler                gcc
  
  C library                 glibc
  
  ARCH                      x86 (generic)
  
  big-endian                no
  
  runtime cpu detection     no
  
  standalone assembly       yes
  
  x86 assembler             nasm
  
  MMX enabled               yes
  
  MMXEXT enabled            yes
  
  3DNow! enabled            yes
  
  3DNow! extended enabled   yes
  
  SSE enabled               yes
  
  SSSE3 enabled             yes
  
  AESNI enabled             yes
  
  AVX enabled               yes
  
  AVX2 enabled              yes
  
  AVX-512 enabled           yes
  
  XOP enabled               yes
  
  FMA3 enabled              yes
  
  FMA4 enabled              yes
  
  i686 features enabled     yes
  
  CMOV is fast              yes
  
  EBX available             yes
  
  EBP available             yes
  
  debug symbols             no
  
  strip symbols             yes
  
  optimize for size         no
  
  optimizations             yes
  
  static                    yes
  
  shared                    no
  
  postprocessing support    no
  
  network support           yes
  
  threading support         no
  
  safe bitstream reader     yes
  
  texi2html enabled         no
  
  perl enabled              yes
  
  pod2man enabled           yes
  
  makeinfo enabled          no
  
  makeinfo supports HTML    no
  
  
  
  External libraries:
  
  openssl
  
  
  
  External libraries providing hardware acceleration:
  
  
  
  Libraries:
  
  avcodec                 avfilter                avformat                avutil
  
  
  
  Programs:
  
  ffmpeg
  
  
  
  Enabled decoders:
  
  
  
  Enabled encoders:
  
  
  
  Enabled hwaccels:
  
  
  
  Enabled parsers:
  
  aac                     h264
  
  
  
  Enabled demuxers:
  
  aac                     h264                    hls                     mpegts
  
  
  
  Enabled muxers:
  
  mov                     mp4
  
  
  
  Enabled protocols:
  
  hls                     http                    https                   tcp                     tls
  
  
  
  Enabled filters:
  
  aformat                 anull                   atrim                   format                  hflip                   null                    transpose               trim                    vflip
  
  
  
  Enabled bsfs:
  
  null
  
  
  
  Enabled indevs:
  
  
  
  Enabled outdevs:
  
  
  
  License: LGPL version 2.1 or later

  It included several filters which I won’t ever need or use, but these filters are pulled in automatically if you don’t specify --disable-avfilter, and specifying --disable-avfilter prevents the ffmpeg binary from being produced. So I’m stuck with those.

  Using these parameters and then running make, I received a binary that was about 5.9 MB in size and looked right :

  $> ldd ffmpeg
  
          not a dynamic executable

  But when I try to run it :

  $> ./ffmpeg -version
  
  Segmentation fault

  Using valgrind to try and inspect the cause of the segmentation fault :

  $> valgrind ./ffmpeg -version
  
  .... lots of stuff ...
  
  ==61362== Jump to the invalid address stated on the next line
  
  ==61362==    at 0x0: ???
  
  ==61362==    by 0x70BB1B: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x70B2E6: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x4033F9: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x1FFF000677: ???
  
  ==61362==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
  
  ==61362==
  
  ==61362==
  
  ==61362== Process terminating with default action of signal 11 (SIGSEGV)
  
  ==61362==  Bad permissions for mapped region at address 0x0
  
  ==61362==    at 0x0: ???
  
  ==61362==    by 0x70BB1B: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x70B2E6: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x4033F9: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x1FFF000677: ???
  
  ==61362==
  
  ==61362== HEAP SUMMARY:
  
  ==61362==     in use at exit: 0 bytes in 0 blocks
  
  ==61362==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
  
  ==61362==
  
  ==61362== All heap blocks were freed -- no leaks are possible
  
  ==61362==
  
  ==61362== For counts of detected and suppressed errors, rerun with: -v
  
  ==61362== Use --track-origins=yes to see where uninitialised values come from
  
  ==61362== ERROR SUMMARY: 93 errors from 90 contexts (suppressed: 0 from 0)
  
  Segmentation fault

  Attempting to access memory at location 0x0 sounds like trying to follow a null pointer. But I’m not sure how to fix this.

  gdb backtrace

  When I first ran gdb ./ffmpeg gdb immediately gave me a segmentation fault and I wasn’t kicked into the gdb REPL, so I couldn’t investigate

  After rebuilding ffmpeg I was able to get in this time :

  $> gdb ./ffmpeg
  
  
  
  GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
  
  Copyright (C) 2018 Free Software Foundation, Inc.
  
  License GPLv3+: GNU GPL version 3 or later /gnu.org/licenses/gpl.html>
  
  This is free software: you are free to change and redistribute it.
  
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  
  and "show warranty" for details.
  
  This GDB was configured as "x86_64-linux-gnu".
  
  Type "show configuration" for configuration details.
  
  For bug reporting instructions, please see:
  
  /www.gnu.org/software/gdb/bugs/>.
  
  Find the GDB manual and other documentation resources online at:
  
  /www.gnu.org/software/gdb/documentation/>.
  
  For help, type "help".
  
  Type "apropos word" to search for commands related to "word"...
  
  Reading symbols from ffmpeg...done.
  
  (gdb) r
  
  Starting program: /src/FFmpeg/ffmpeg
  
  warning: Error disabling address space randomization: Operation not permitted
  
  
  
  Program received signal SIGSEGV, Segmentation fault.
  
  0x0000000000000000 in ?? ()
  
  (gdb) bt
  
  #0  0x0000000000000000 in ?? ()
  
  #1  0x0000000000f9a8d5 in __register_frame_info_bases.part.6 ()
  
  #2  0x00000000004445fd in frame_dummy ()
  
  #3  0x0000000000000001 in ?? ()
  
  #4  0x0000000000ebd20c in __libc_csu_init ()
  
  #5  0x0000000000ebc9d7 in __libc_start_main ()
  
  #6  0x000000000044451a in _start ()
  
  (gdb)

  I tried grep’ing the code base for __register_frame_info_bases and found nothing. So I’m not really sure where to go from here

  A fix, but not an explanation

  By randomly removing configuration parameters and rebuilding I discovered that --disable-pthreads was causing the segmentation fault. When I remove this, ffmpeg runs just fine

  I don’t know why this is the case, though. Why would they make it possible to remove something that you need to run ?

• 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”.