multimedia

问题 I am implementing a video player using ffmpeg multimedia framework. I am able to achieve play, pause, increase speed, decrease speed, forward seek, backward seek functionalities. But reverse playback of the video is not so smooth, it stutters a lot. Please help me in understanding video reverse playback. What is the better approach for this? Is there any other multimedia framework which support reverse video playback? Many thanks in advance. 回答1: So, first, some framing of this issue. FFmpeg

问题 Since MJPEG over http consists basically on the transmission of a series of JPEG images seperated by a defined seperator, how does MPlayer recognize that it is an MJPEG stream? Thank you 回答1: Have a look at: MplayerMjpegStreamViewing < Motion < Foswiki e.g. mplayer -fps 4 -demuxer lavf http://rpi-6:8080/?action=stream does the job for me. Suitable for a streaming server running on a Raspberry like this: /usr/local/bin/mjpg_streamer -o output_http.so -w ./www -i input_raspicam.so -x 1920 -y

问题 I have implemented a Videoplayer using Qt5.1 QMediaPlayer, however I would like to know if there is a way to control the buffer sizes for streaming media from a URL so as to cater for different connection speeds. In addition, is there a way to determine how much of the content being streamed has been completely downloaded. 回答1: The buffer size is based on the keyframes contained in the video track, the range between 2 keyframes defines the size of each buffered piece and as far as I know this

问题 I have implemented a Videoplayer using Qt5.1 QMediaPlayer, however I would like to know if there is a way to control the buffer sizes for streaming media from a URL so as to cater for different connection speeds. In addition, is there a way to determine how much of the content being streamed has been completely downloaded. 回答1: The buffer size is based on the keyframes contained in the video track, the range between 2 keyframes defines the size of each buffered piece and as far as I know this

问题 I am evaluating a migration from Qt 4.8 towards Qt 5.2 and the most important point is the multimedia backend. In Qt 5.2 there are some important features the Phonon backend in Qt 4.8 does not provide. But at least the elder version showed subtitles (SRT file in the same directory as the video file). Neither the documentation nor the trial-and-error provided me any results. So, does anyone know how to FORCE Qt 5 to show these subtitles? Or isnt it even supported (would be a shame) Any help is

问题 I am trying to read data from multiple microphones in Linux (ubuntu 14.04). I have a specific constraint that the reading from microphones should be via polling(so no waiting until there is data, although the data comes in high frequency). I wanted to know if that is possible in Linux? Unfortunately audio capture is not the area of my expertise and I would like to know if the choice of using Alsa is a good one. To better understand the problem, here is a pseudo-code that I had in mind: open

问题 I'm looking to change the speed of a sound file, but am at a loss as to how to accomplish it. I'm assuming that some type of interpolation has to take place in the case of slowing it down, but am unsure how to accomplish a speed up - perhaps an average of several samples? Whether it changes the tempo or pitch doesn't really matter at the moment, I'd like to learn how to accomplish both, but would like to at least accomplish one or the other to begin. If anyone has any references to the math

问题 I want put rotation information into my mp4 video file but I have no idea about this. Is there any program that I can add "rotation" metadata? It would be OK if there's the way to edit video content with hexa editor. 回答1: +1 for FFMpeg. More specifically, I had good results correcting orientation metadata with ffmpeg -i input.mp4 -metadata:s:v rotate=90 -vcodec copy -acodec copy output.mp4 回答2: Check out the software FFMpeg, use ffprobe to give you the rotation metadata of any video file if

问题 I want put rotation information into my mp4 video file but I have no idea about this. Is there any program that I can add "rotation" metadata? It would be OK if there's the way to edit video content with hexa editor. 回答1: +1 for FFMpeg. More specifically, I had good results correcting orientation metadata with ffmpeg -i input.mp4 -metadata:s:v rotate=90 -vcodec copy -acodec copy output.mp4 回答2: Check out the software FFMpeg, use ffprobe to give you the rotation metadata of any video file if

问题 In html 5, I want to embed an mp4 like this: <video width="640" height="480" controls> <source src="somefile.mp4" type="video/mp4"> Your browser does not support the video tag. </video> The video runs fine the the browser in my development machine, but the file is 500MB because it was recorded in full HD. How do I down-sample the file so that it is about 50MB, with smaller video but the same sound quality, and still able to play in the browser using the html5 video tag shown above? I am using