Hi all, I have some doubts on liveMedia regarding RTSP audio & video synchronization.
We have developed a streaming application using live555 library to stream via RTSP. It works like charm when streaming only one stream per session (audio or video). However, problems appear when I try to stream both audio and video using the same RTSP session. I tried playing it using VLC and it only plays the video. In debug mode, it shows this message continuously: core audio output warning: buffer too late (-541608 us): dropped In order to understand this behaviour I used the testRTSPClient as RTSP client, modified to print also the Normal Play Time. What I could observe is that Presentation Times of both audio and video streams are respectively coherent between them. However, after some seconds running, there is an abrupt change in Presentation Time of one of the streams (usually audio), which I suppose that corresponds to RTCP synchronization. After that, there is a big gap between video and audio NPT which remains there during all the transmission, taking sometimes negative values. This is the testRTSPClient output (the timestamp gap can be observed): Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.033291 NPT: 2.911316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.033291 NPT: 2.911316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.053291 NPT: 2.931316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.053291 NPT: 2.931316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.073291 NPT: 2.951316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.073291 NPT: 2.951316 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 1780 bytes. Presentation time: 1410784970.163530 NPT: 3.041563 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 3093 bytes. Presentation time: 1410784970.163530 NPT: 3.041563 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 9393 bytes. Presentation time: 1410784970.163530 NPT: 3.041563 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 5410 bytes. Presentation time: 1410784970.163530 NPT: 3.041563 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.093291 NPT: 2.971316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.093291 NPT: 2.971316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.113291 NPT: 2.991316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.113291 NPT: 2.991316 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 1731 bytes. Presentation time: 1410784977.533251 NPT: 10.411284 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 3474 bytes. Presentation time: 1410784977.533251 NPT: 10.411284 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 11707 bytes. Presentation time: 1410784977.533251 NPT: 10.411284 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 8298 bytes. Presentation time: 1410784977.533251 NPT: 10.411284 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.133291 NPT: 3.011316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.133291 NPT: 3.011316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.153291 NPT: 3.031316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.153291 NPT: 3.031316 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 2468 bytes. Presentation time: 1410784977.574917 NPT: 10.452950 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 4043 bytes. Presentation time: 1410784977.574917 NPT: 10.452950 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 12999 bytes. Presentation time: 1410784977.574917 NPT: 10.452950 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 9043 bytes. Presentation time: 1410784977.574917 NPT: 10.452950 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.173291 NPT: 3.051316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.173291 NPT: 3.051316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 1436 bytes. Presentation time: 1410784970.193291 NPT: 3.071316 Stream "rtsp://192.168.10.77:8554/S22J/"; audio/PCMU: Received 484 bytes. Presentation time: 1410784970.193291 NPT: 3.071316 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 3153 bytes. Presentation time: 1410784977.616583 NPT: 10.494616 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 3766 bytes. Presentation time: 1410784977.616583 NPT: 10.494616 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 6609 bytes. Presentation time: 1410784977.616583 NPT: 10.494616 Stream "rtsp://192.168.10.77:8554/S22J/"; video/H264: Received 4695 bytes. Presentation time: 1410784977.616583 NPT: 10.494616 I checked the RTP timestamps (in transmission) and everything seems OK (no gaps and coherent between them). This behaviour is not the one I would expect and I think it is exactly what's happening when I try to play the session using VLC. So my question is what do you think is happening here and how do you think I can solve this issue? I have the feeling that I do something wrong in transmission (maybe defining the Presentation Time) but I can't see what. Thanks in advance for any hint, Kind regards, -------------------------------------------------------- Gerard Castillo Lasheras Enginyer de Projectes Fundació i2CAT - Unitat Audiovisual SkypeID: gerardcl85 Telf.: +34.93.553.25.48 --------------------------------------------------------
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