I use live555 to receive RTP video frame (frame encoded in H264). I use Live555 open my local .sdp file to receive frame data. I just saw DummySink::afterGettingFrame was called ceaselessly。 if fReceiveBuffer in DummySink is correct, Why FFMPEG cannot decode the frame? My code is wrong?
Here is my Code Snippet:
http://paste.ubuntu.com/12529740/
the function avcodec_decode_video2 is always return failed , its value less than zero
fReceiveBuffer is present one video frame？
Oh, Here is my FFMPEG init code need to open related video decoder:
http://paste.ubuntu.com/12529760/
I read the document related H264 again， I found out that I-frame(IDR) need SPS/PPS separated by 0x00000001 insert into the header and decoder have a capacity to decode the frame correctly. Here is a related solution
FFmpeg can't decode H264 stream/frame data
Decoding h264 frames from RTP stream
and now, My App works fine, it can decode the frame and convert it to OSD Image for displaying to screen .
Related
I've a 16bit greyscale video stream from a LWIR (thermal camera) and I want to forward the stream over RTP without any compression.
gstreamer format is: video/x-raw,format=GRAY16_LE,width=640,height=520,framerate=9/1
But I can't find any plugin to transmit the data over RTP.
https://gstreamer.freedesktop.org/documentation/rtp/index.html?gi-language=c
Do you have an idea?
Thanks, Martin
Check for the specs of uncompressed video data over RTP:
https://www.rfc-editor.org/rfc/rfc4175
As you will notice your specific format is not covered by the specification.
I've written a C++ converter based on FFMpeg which can receive a link to hls-stream and convert it into local .mp4 video. So far, so good, converter works like a charm, no questions about that.
PROBLEM: No matter what input source I'm providing to the converter, at the end of convertation I need to receive video with key-frames ONLY. I need such video due to perfect seeking forward and reverse.
It's a well-known fact that subsidiary video frames (P and B) dependent on their owner-frame (I frame), because this frame contains full pixel map. According to that, we can recreate a I frame for each P and B frame by merging their data with their I frame. That's why such ffmpeg command ffmpeg -i video.mp4 output%4d.jpg works.
QUESTION: How can I implement an algorithm of merging of frames in order to recreate Key-frames ONLY video at the end? What kind of quirks I need to know about merging datas of AVPackets?
Thanks.
You cannot "merge" P and B-frames of a compressed stream (e.g. with H.264 codec), to obtain I-frames.
What ffmpeg does with
ffmpeg -i video.mp4 output%4d.jpg
is decoding each frame (thus it needs to start from an I-frame, then decode all subsequent P and B-frames in the stream), and compress them back to JPEG and output a JPEG image for each frame in the original input stream.
If you want to convert an input stream with P/B frames to an intra-only stream (with all I-frames), you need to transcode the stream.
That means decode all frames from the original stream and encode them back to an intra-only stream.
I am having a task to build a decoder that generates exactly 1 raw audio frame for 1 raw video frame, from an encoded mpegts network stream, so that users can use the API by calling getFrames() and receive exactly these two frames.
Currently I am reading with av_read_frame in a thread, decode as packets come, audio or video; collect until a video packet is hit. Problem is generally multiple audio packets are received before video is seen.
av_read_frame is blocking, returns when certain amount of audio data is collected (1152 samples for mp2); and decoding that packet gives a raw AVFrame having duration of T (depends on samplerate); whereas the video frame generally has duration bigger than T (depends on fps), so multiple audio frames are received before it.
I was guessing I have to find a way to merge collected audio frames into 1 single frame just when video is hit. Also resampling and setting timestamp to align with video is needed I guess. I don't know if this is even valid though.
What is the smoothest way to sync video and audio in this manner ?
I'm using FFMPEG to decode video stream from IP Camera, I have the example code that can decode video stream with any codec into YUI frames format.
But my case is special, I will describe as below
The IP camera stream is MJPEG, and I want using FFMPEG to decode, but I don't want to decode frame into YUV, I want to decode frame under jpeg format, and save those jpeg buffer into image files (*.jpg).
So far, I can do it by converting YUV frame (after decoding) to Jpeg, but this will cause bad performance. Since video stream is MJPEG, I think I can get jpeg data before decoding to YUI, but I don't know how to do it.
Someone can help me?
Many thanks,
T&T
I use Live555 h.264 stream client to query the frame packets from an IP camera, I use ffmpeg to decode the buffer and analysis the frame by OpenCV.(those pipeline are based on testRTSPClient sample, I decode the h.264 frame buffer in DummySink::afterGettingFrame() by ffmpeg)
And now I wanna stream the frame to another client(remote client) OnDemand mode in real-time, the frame may added the analysis result(boundingboxs, text, etc), how to use Live555 to achieve this?
Well, your best bet is to re-encode the resultant frame (with bounding boxes etc), and pass this to an RTSPServer process which will allow you to connect to it using an rtsp url, and stream the encoded data to any compatible rtsp client. There is a good reference on the FAQ for how to do this http://www.live555.com/liveMedia/faq.html#liveInput which walks you through the steps taken, and provides example source code which you can modify for your needs.