Newest 'ffmpeg' Questions - Stack Overflow

Les articles publiés sur le site

• FFmpeg API : parse raw movie packet data into AVPacket

  7 novembre 2011, par Andrea3000

  If you have a movie file and you need to extract frame (packet) from it, it's simply a matter of writing:

  avformat_open_input(AVFormatContext **ps, const char *filename, AVInputFormat *fmt, AVDictionary **options);
  
  ...
  
  AVPacket packet;
  av_read_frame(formatContext, &packet);
  

  But what if I don't have the movie file but only unparsed, raw packet data? These raw packet data are the same as the raw data contained into the movie file but I don't access them throught avformat_open_input and therefore I can't use av_read_frame so FFmpeg doesn't parse them.

  How can I parse this raw data in order to build the corresponding AVPacket? I need to obtain an AVPacket identical to the ones provided by av_read_frame.

• Video encoding libraries for iOS

  7 novembre 2011, par peetonn

  I really stucked with that problem, because I haven't seen enough information in the internet regarding video encoding in iOS, however we can observe plenty of apps that deal with the problem of video streaming successfully (skype, qik, justin.tv, etc.)
  I'm going to develop an application, that should send video frames obtained from camera and encoded in h.263 (h.264 or MPEG-4 it is under decision) to a web-server. For this, I need some video encoding library. Obviously, ffmpeg can deal with that task, but it is under LGPL license, which could probably lead to some problems in submitting the app in the AppStore. On the other hand, there are some applications, which are seemed to use ffmpeg library, but only Timelapser clearly states this fact in app description. Does this mean, that other apps are not using ffmpeg or just hiding this information?

  Please, share your thoughts and experience in this topic. I'm open for dicsussion.

• Windows Phone 7.1 Video (3GP,MP4) to Audio (MP3) Converter — ffmpeg on windows phone ?

  7 novembre 2011, par Hypi

  Is there a way to convert Video (3GP,MP4,etc) files stored in isolated storage of a windows phone 7.1 app to a Audio (MP3) file?

  I initially thought ffmpeg can do something like this but I can't find a Windows Phone compatible Wrapper. Is there a library I can use or a similar one?

• Disadvantages to creating/removing many hard links ?

  6 novembre 2011, par agartland

  I need to create hundreds to thousands of temporary hard or symbolic links that will be deleted shortly after creation. For my purposes both types of links will work (i.e. the target is not a directory and it always exists on the same file system)

  As I understand it, symbolic links create a small file that contains the path to the original file. Whereas a hardlink creates a reference to the data in the same inode. So maybe if I am going to be creating/deleting thousands of these links is it better to be creating and deleting thousands of tiny files (symlinks) or thousands of these references (hardlinks)? It seems like one taxes the hard drive (maybe fragmentation) while the other might tax the file system itself? Where are inode references stored. Do I risk corrupting the file system by making so many hard links? What about speed?

  Thanks for your expertise!

  This a work around to be able to use ffmpeg to encode a movie out of an arbitrary subset of images from a directory. Since ffmpeg requires that the files be named properly (e.g. frame%04d.jpg) I realized I can just create hard/sym links to the subset of files and just name the links appropriately. This avoids renaming the original files and having to actually copy the data. It works great but it requires creating and deleting many thousands of links, repeatedly.

  Sort of addresses this problem too I believe: convert image sequence using ffmpeg

• How to extract audio from a video with ffmpeg in C++ ?

  6 novembre 2011, par Gp2mv3

  I'm using FFmpeg to extract informations about a video file. But i want to extract the audio channels to read it with FMOD.

  How can I do that ? Is it simple ?

  Do you know a good tutorial about FFmpeg in C++ ?

  Thanks