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• Nginx Live transcoding with ffmpeg

  7 mars 2015, par Stian Tofte

  I’m live streaming video to my server(It’s external somewhere in the world).
  And what I’m trying to do here, is that my server will transcode the input to a lower bitrate before it pushes it to the video site like twitch and so on.

  And I’m doing this on windows. I have tried to google around watched youtube videos. and so on.. But couldn’t find any solution for it. So here is what I have at this moment(not working).

  In my nginx.conf :

  rtmp {
  
  server {
  
      listen 1935;
  
      chunk_size 8192;
  
  
  
      application code {
  
          live on;
  
  
  
      }
  
  
  
      application twitch {
  
          push rtmp://live-ams.twitch.tv/app/live_xxxxxxxxxxxxxxxxx;
  
      }
  
  }

  So here the application code is receving the stream from my computer at home. I’m using ffmpeg to transcode it.

  And here is my batch file(That I have to start manualy. Can’t start it within the config of nginx on windows.)

  ffmpeg -i rtmp://localhost/code -vcodec flv -acodec copy -s 1280x720 -f flv rtmp://localhost/twitch
  
  pause

  Right now It’s just downscaling but that is okay. So this is supposed to send the stream back to the "twitch" application in my nginx config. And then nginx will stream it to twitch.

  But when I launch my ffmpeg bat file.. I get this :
  

  So it’s here my road ends. Anyone knows how to do this ?

  Thanks in advance :) Stian

• Files dissapearing with ffmpeg recursive conversion

  13 août 2014, par CaRoXo

  I started in askubuntu, asking for a way to convert recursively more than 14K of wma to mp3 extracting the wma files path from a txt file.
  There was an answer that could cover my needs, but a bug appears. The first run with some hundreds worked ok. The second, some wma albums got converted, others entirely deleted. There were some modifications. And last time completely, deleted all wma without converting.

  this was the original script

  #!/usr/bin/env bash
  
  
  
  readarray -t files < wma-files.txt
  
  
  
  for file in "${files[@]}"; do
  
      out=`echo $file | sed "s:wma:mp3:"`
  
      probe=`avprobe -show_streams "$file" 2>/dev/null`
  
      rate=`echo "$probe" | grep "bit_rate" | sed "s:.*=\(.*\)[0-9][0-9][0-9][.].*:\1:"`
  
      avconv -i "$file" -ab "$rate"k "$out"
  
      rm "$file"
  
  done

  Then the adaptation with ffmpeg

  #!/usr/bin/env bash
  
  
  
  readarray -t files < wma-files.txt
  
  
  
  for file in "${files[@]}"; do
  
      out=`echo $file | sed "s:wma:mp3:"`
  
      probe=`avprobe -show_streams "$file" 2>/dev/null`
  
      rate=`echo "$probe" | grep "bit_rate" | sed "s:.*=\(.*\)[0-9][0-9][0-9][.].*:\1:"`
  
      ffmpeg -i "$file" -ab "$rate"k "$out" && rm "$file"
  
  done

  With the first one I converted many files. Other just get deleted. The ones deleted were always the same release (so, all tracks from a release). I can listen, and even convert them with Soundkonverter.

  Both of them produces "no such file of directory" and when this happens, everything get deleted.

  The partition where files are stored is a usb HDD ntfs, but also happens in my ext4 internal HD.
  Im under Xubuntu 14.04

  Here the script running with avconv (wich what i managed to convert some, but other get dissapeared) http://pastebin.com/w5weqEws and with ffmpeg (that didn’t convert any) http://pastebin.com/3QkaPzvW

  I can’t find differences between successfully and deleted original wma’s. But for example, while other progs like beets read and write the tags, puddletag and mp3tag (under wine) don’t, until I converted them with soundkonverter.

  As the person trying to help me there redirect me here on the original post http://askubuntu.com/questions/508278/how-to-use-ffmpeg-to-convert-wma-to-mp3-recursively-importing-from-txt-file/508304#508304
  Im here asking for any help to make run an script like this. Or any to use ffmpeg to convert recursively the audio files. My capacity of understanding is short for being able to make something working just reading the docs.

  So I ask a help to run this. If I miss any relevant information, just tell me.

  NOTE : I want to add that doing the conversion with

  for file in "${files[@]}"; do
  
      out=`echo "$file" | sed s:wma:mp3:`
  
      avconv -i "$file" -ab 192k "$out"
  
      rm "$file"
  
  done

  It works in the same files (the ones that are deleted with the other). Only that it makes everything to 192k, so not good if Im converting lower bitrate ones. And get this error "Application provided invalid, non monotonically increasing dts to muxer in stream 0" that seems something typical from avconv in 14.04. With ffmpeg I cant try becouse I don’t find the way how to use it, even out of the script. I really don’t understand the docs seems
  .

  NOTE2 : This is a mediainfo exit from :

  1- A typical wma that get dissapeared always with the script

  Audio
  
  ID                                       : 1
  
  Format                                   : WMA
  
  Format version                           : Version 2
  
  Codec ID                                 : 161
  
  Codec ID/Info                            : Windows Media Audio
  
  Description of the codec                 : Windows Media Audio 9 - 128 kbps, 44 kHz, stereo 1-pass CBR
  
  Duration                                 : 2mn 25s
  
  Bit rate mode                            : Constant
  
  Bit rate                                 : 128 Kbps
  
  Channel(s)                               : 2 channels
  
  Sampling rate                            : 44.1 KHz
  
  Bit depth                                : 16 bits
  
  Stream size                              : 2.21 MiB (99%)
  
  Language                                 : English (US)

  2- A Wma that got succesfully converted (yes Im using copies now, I cant risk specially some rares audios that I got on the road)

  Audio
  
  ID                                       : 1
  
  Format                                   : WMA
  
  Format version                           : Version 2
  
  Codec ID                                 : 161
  
  Codec ID/Info                            : Windows Media Audio
  
  Description of the codec                 : Windows Media Audio 9 - 128 kbps, 44 kHz, stereo 1-pass CBR
  
  Duration                                 : 4mn 35s
  
  Bit rate mode                            : Constant
  
  Bit rate                                 : 128 Kbps
  
  Channel(s)                               : 2 channels
  
  Sampling rate                            : 44.1 KHz
  
  Bit depth                                : 16 bits
  
  Stream size                              : 4.21 MiB (99%)
  
  Language                                 : English (US)

  So, as I don’t see difference, but maybe, I’m losing any data to look into ?

• Of ctors and dtors

  18 février 2011, par Multimedia Mike — Programming, Sega Dreamcast

  I haven’t given up on the Sega Dreamcast programming. I was able to compile a bunch of homebrew code for the DC many years ago and I can’t make it work anymore. Again, I was working with a purpose-built, open source RTOS named KallistiOS (or KOS). I can make the programs compile but not run. I had ELF files left over from years ago which still executed. But when I tried to build new ELF files, no luck— the programs crashed before even reaching my main() function.

  I found the problem : ELF files are comprised of a number of sections and 2 of these sections are named ’.ctors’ and ’.dtors’ which stand for constructors and destructors. The KOS RTOS performs a manual traversal of .ctors section during program initialization and this is where things go bad. The traversal code doesn’t seem to account for a .ctors section that only contains a single entry. I commented out the function that does the traversal and programs started to work, at least until it was time to exit the program and return control to the program loader. That’s when the counterpart .dtors section traversal code ran and demonstrated the same problem. I’ll exhibit the problematic code at the end of this post.

  So I’m finally tinkering with Sega Dreamcast programming once again and with a slightly better grasp of software engineering than the first time I did this.

  Portable and Compatible C ?
  If nothing else, this low-level embedded stuff exposes you to some serious toolchain arcana, the likes of which you will likely never see working strictly in the desktop arena.

  Still, this exercise makes me wonder why C code from a decade ago doesn’t compile reliably now. Part of it is because gcc has gotten stricter about the syntax it will accept. In the case of this specific crashing problem, I suspect it comes down to a difference in the way the linker generates the final ELF file. I’ve written a list of items I have had to modify in the KOS codebase in order to get it to compile on more recent gcc versions. I wonder if it would be worth publishing the specifics, or if anyone would ever find the information useful ? Oh, who am I kidding ? Of course I’ll write it up, perhaps publish a new version of the code, if only because that’s the best chance I have of finding my own work again some years down the road.

  Problematic C Code
  See if this code makes any sense to you. It somehow traverse a list of 32-bit function pointers (in different directions, depending on constructors or destructors), executing each in turn. However, it appears to fall over if the list of pointers consists of a single entry.
  

  PLAIN TEXT

  C :

  1. typedef void (*fptr)(void) ;
  2.  
  3. static fptr ctor_list[1] __attribute__((section(".ctors"))) = { (fptr) -1 } ;
  4. static fptr dtor_list[1] __attribute__((section(".dtors"))) = { (fptr) -1 } ;
  5.  
  6. /* Call this to execute all ctors */
  7. void arch_ctors() {
  8.     fptr *fpp ;
  9.  
  10.     /* Run up to the end of the list (defined by crtend) */
  11.     for (fpp=ctor_list + 1 ; *fpp != 0 ; ++fpp)
  12.          ;
  13.  
  14.     /* Now run the ctors backwards */
  15.     while (—fpp> ctor_list)
  16.         (**fpp)() ;
  17. }
  18.  
  19. /* Call this to execute all dtors */
  20. void arch_dtors() {
  21.     fptr *fpp ;
  22.  
  23.     /* Do the dtors forwards */
  24.     for (fpp=dtor_list + 1 ; *fpp != 0 ; ++fpp )
  25.         (**fpp)() ;
  26. }