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• how to read a http video stream with libavcodec (ffmpeg)

  23 décembre 2011, par mwahab

  I'm trying to read a real-time http video stream (I've set one up using VLC and my webcam) using libavcodec from ffmpeg. so far I've been able to read an mpeg file fine but when I pass a url instead of the file name it hangs (I assume it's waiting for the end of the file).

  anyone have experience/ideas on how to do this ? I'm also open to alternatives if people have other suggestions.

  the end goal is to do live video-streaming on the iphone. apple's http live streaming has too much lag for what I need but that's for another post :)

  any help is greatly appreciated !

• 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

• FFmpeg decoding H264

  25 septembre 2011, par Steve McFarlin

  I am decoding a H264 stream using FFmpeg on the iPhone. I know the H264 stream is valid and the SPS/PPS are correct as VLC, Quicktime, Flash all decode the stream properly. The issue I am having on the iPhone is best shown by this picture.

  

  It is as if the motion vectors are being drawn. This picture was snapped while there was a lot of motion in the image. If the scene is static then there are dots in the corners. This always occurs with predictive frames. The blocky colors are also an issue.

  I have tried various build settings for FFmpeg such as turning off optimizations, asm, neon, and many other combinations. Nothing seems to alter the behavior of the decoder. I have also tried the Works with HTML, Love and Peace releases, and also the latest GIT sources. Is there maybe a setting I am missing, or maybe I have inadvertently enabled some debug setting in the decoder.

  Edit

  I am using sws_scale to convert the image to RGBA. I have tried various different pixel formats with the same results.

  sws_scale(convertCtx, (const uint8_t**)srcFrame->data, srcFrame->linesize, 0, codecCtx->height, dstFrame->data, dstFrame->linesize);

  I am using PIX_FMT_YUV420P as the source format when setting up my codec context.