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• Convert video from FFMPEG than video is rotated [duplicate]

  25 octobre 2016, par user7050166

  This question already has an answer here :

  • video captured from iphone gets rotated when converted to .mp4 using ffmpeg
    
    8 answers
    

  I have created one Application API, in this Application API When i have upload video from file manager than video is rotated but when i have capture and direct upload than video is perfect work.

  i have use this command transpose=1 but capture video is rotated 90 degree when upload and if i have remove this command than file manager video is rotated.

  so please give me solutions.

  /usr/bin/ffmpeg -i video.mp4 -i watermark.png -filter_complex 'overlay=10:10' -s 640x1280 -b 512k -vcodec mpeg1video -acodec copy -vcodec h264 -acodec aac -strict -2 output_video.mp4

  file manager upload video is auto rotated on 270 degree, i have not use any rotated command but capture video is work perfect.

• iOS Video Player FFmpeg

  13 février 2013, par Rahim Jan

  So I want to make an app for the iPhone that will play live mms :// video streams.

  I have look around, and everywhere says that I'll need FFmpeg in order to accomplish it. So I successfully compiled the FFmpeg libraries, but now

  Do I have to convert the mms :// link to a .m3u8 link ? Or I can just use apples AV Foundation Framework ?

  Thanks !

• Can I know which byte range to read from a remote mp4 file for FFMpeg to decode a keyframe ?

  12 octobre 2023, par db9117

  I need to decode a of keyframe of a video file (mp4, h264 encoded). I know the timestamp of the keyframe I want to extract/decode. I want to minimize amount of data being read in memory. For this, I need to know beforehand exactly the minimal byte range I would require that encompasses this keyframe. How do I know what is the minimal byte range in the whole mp4 byte stream I need to read in order to be able to decode the keyframe ?

  


  I currently find the appropriate keyframe in the index_entries contained in the header. I get its byte position (pos attribute) and timestamp (timestamp attribute). I calculate the range as follows :

  


  startBytes : minimum of :

  


  

  1. the pos of the keyframe

  


  2. the pos of the nearest index entry in the audio stream happening at or before the keyframe's timestamp.

  


  


  This way when it's decoding the frame, if it also needs the audio content for demuxing, it would have it.

  


  endBytes : maximum of :

  


  

  1. the pos of the next frame in the video stream's index, after the keyframe

  


  2. the pos of the next frame in the audio stream's index after the timestamp of the wished keyframe.

  


  


  This way I know that I have everything up until the next frame in the index, which theoretically should be enough to decode the keyframe only.

  


  I then read the appropriate byte range.

  


  When I try to decode the frame, I run in a loop until I succeed :

  


  

  • avcodec_read_frame

  


  • avcodec_send_packet

  


  • avcodec_receive_frame

  


  


  I ignore AVERROR(EAGAIN) errors.

  


  avcodec_receive_frame fails multiple times with error AVERROR(EAGAIN) which I ignore, until it fails saying that the memory it wants to read isn't available (wants to read after endBytes). I explicitly tell it to fail if it wants to read more than it has already read.

  


  Note : for other keyframes at other positions in other videos, it sometimes succeeds (probably because the range is big enough by chance), but it fails more often than not.

  


  My question is : Why is the end of the range not enough to be able to decode only the one keyframe ? Is there any way to more precisely calculate the exact range in bytes I would need in order to decode a particular keyframe ?