Newest 'ffmpeg' Questions - Stack Overflow

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• Asking ffmpeg to extract frames at the original frame rate

  28 septembre 2011, par intrpc

  On the ffmpeg documentation (here, and here) I read that, by default, ffmpegchoses to extract frames at 25 frames per second (otherwise you can specify a framerate with the -r option)

  My problem is that I have a folder with dozens of videos, each of them recorded at different frame rates, so my question is:

  Is there a way to ask ffmpeg to extract frames from a video at the "native" frame rate (i.e. the original frame rate at which the video was recorded)?

  In case it matters, I am working with MP4 files

• Convert dat file from vcd to mpeg on ubuntu [closed]

  28 septembre 2011, par Silver Moon

  mencoder and vcdxrip can be used to rip a vcd into mpeg on ubuntu.

  But I want to convert a .dat file to .mpg/.mpeg

  cdxa2mpeg is able to convert .dat to .mpg on windows , but on ubuntu it says

  ++ WARN: unknown chunk id [] encountered

  can ffmpeg convert a .dat file to .mpeg ?

  using a command like this :

  ffmpeg -i avseq01.dat -pix_fmt yuv420p -vcodec mpeg1video happy.mpeg

  says :

  picture size invalid (0x0) Cannot allocate temp picture, check pix fmt

  Any other ideas ?

• Multiple video sources combined into one

  28 septembre 2011, par Oded

  I am looking for an efficient way to do the following:

  Using several source videos (of approximately the same length), I need to generate an output video that is composed of all of the original sources each running in its own area (like a bunch of PIPs in several different sizes). So, the end result is that all the original are running side-by-side, each in its own area/box.

  The source and output need to be flv and the platform I am using is Windows (dev on Windows 7 64bit, deployment to Windows server 2008).

  I have looked at avisynth but unfortunately it can't handle flv and non of the plugins and flv splitters I have tried worked.

  My current process uses ffmpeg in the following manner:

  1. Use ffmpeg to generate 25 png's per second per video, resizing the original as needed.
  2. Use the System.Drawing namespace to combine each set of frames into a new image, starting with a static background, then loading each frame into an Image and drawing to the background Graphics object - this gives me the combined frames.
  3. Use ffmpeg to combine the generated images to a video.

  All this is very IO intensive (which is my processing bottleneck at the moment) and I feel there must be a more efficient way to reach my goal. I do not have much experience with video processing, and don't know what options are out there.

  Can anyone suggest a more efficient way of processing these?

• Incompatible Pointer Type Error, sws_scale, ffmpeg

  28 septembre 2011, par James Felix Black

  My code is very straightforward; it consumes YUV420P data, resizes it, and produces a PNG or JPEG image (OS X Lion, Apple's gcc 4.2.1). It works fine; I'm using ffmpeg (HEAD, as of mumble days ago), but when running in -pedantic-errors mode (which I like to do from time to time):

  zc_libav.c:30: error: passing argument 2 of ‘sws_scale’ from incompatible pointer type
  

  Ouch! Well, what's my code look like?

  sws_scale(sws_ctx, 
            in_pic->data,
            in_pic->linesize, 
            0, 
            in->y, 
            out_pic->data, 
            out_pic->linesize); 
  

  (You can assume for the sake of argument that the in_pic and out_pic AVPicture structures have been properly initialized, as the code works).

  Well, what're the offending data types?

  from libswscale/swscale.h:

  int sws_scale(struct SwsContext *c, const uint8_t* const srcSlice[], …
  

  from libavcodec/avcodec.h

  typedef struct AVPicture {
    uint8_t *data[4];
    int linesize[4];       ///< number of bytes per line
  } AVPicture;
  

  As I noted above, when I change -pedantic-errors to -pedantic, I get the same complaint, but the code compiles and runs correctly. For my own neurotic sanity, is there any way to get the advantages of -pedantic-errors and, you know, compile this code?

• H.264 (MP4) video not play in IE9, but will play in Safari [closed]

  27 septembre 2011, par Austin S

  I have encoded a video using FFMPEG into three formats: WebM, MP4, and FLV. Chrome, Mozilla, and theoretically Opera (although I haven't tested it) should all use the WebM version. IE9, iOS devices, and Adriod should use the MP4 container. While all legacy browsers should default back to the flash version of the file. I'm using video-js to help serve the content. The content is set to preload and autoplay.

  I have found that everything is working as intended except for IE9, where all I get is the poster image and a white dot that typically spins indicating that the file is loading however it is not spinning in this scenario. The MP4 file opens in Safari, an iPad, an iPhone, and an Andriod - verifying that the file is infact legit.

  The following is the specs for the MP4 file when I stream it using VLC. I don't know if this is particularly useful, I'm just trying to provide as much detail as possible.

  VLC Codec Details

  • Stream 0

    Type: Video

    Codec: MPEG-4 Video (mp4v)

    Language: English

    Resolution: 480x270

    Frame rate: 2997

  • Stream 1

    Type: Audio

    Codec: MPEG AAC Audio (mp4a)

    Language: English

    Channels: Stereo

    Sample rate: 48000 Hz

  When accessing videojs.com from my coworkers computer, the video on their main page wouldn't play the video correctly in IE9, but we could hear the audio. When I went to another coworkers computer it played just fine. I'm wondering if IE9, or video-js, is tempermental depending on how updated your OS is.

  The fact that I'm working on XP with IE7 is making this all the more difficult to fix, so if you have any suggestions on what could point me in the right direction, I would greatly appreciate it!

  Thanks,

  Austin S