Ross and Community, In regards to the Trick Mode Data Rate discussion last year. A few posts thus far have observed 'trick play' data rates higher than that of the source media and a desire to throttle the data rate to some preset maximum limit. Please reference the following related posts from March-July 2007.
http://lists.live555.com/pipermail/live-devel/2007-March/006317.html http://lists.live555.com/pipermail/live-devel/2007-April/006509.html http://lists.live555.com/pipermail/live-devel/2007-July/007210.html >As previously dscussed on this mailing list, we have a solution in >mind (it will require updating the index file format to include a new >'duration' field, and implement a new Transport Stream 'framer' class >that uses this). There is currently no ETA for this, though. Has there been any progress in this regard? I am using Live555 version 0.19 source and have found that the average 'trick play' data rate for scales greater than 1X is more than double that of the original source media. The actual data rate seen for a 10Mbit/sec stream in trick play averages 22Mbit/sec for the following selected scales: 2X, 4X, 8X, 16X and 64X. Testing below 1X shows the data rate to fall below that of the original source media. At a scale of 1/2X, the resulting data rate was 7.3Mbps for a 10Mbps stream. My goal is to limit the playback data rate so that it is no greater than that of the source media at 1X. Ross states in his April 2007 response to "HD MPEG2 TrickPlay" , that: Two methods were used to obtain the results above. (Note that in both test methods, the Live555 server in use has been modified to accept the "scale" parameter from stdin upon stream open since VLC, to my knowledge, doesn't let you pick the scale). First OpenRTSP was used on the same host as the server to dump the streamed output to a file using the following command: openRTSP.exe -d 34 -Ftwo_x_scale rtsp://127.0.0.l/tek.ts The source stream is 10Mbps. Live555 is commanded to stream at a scale of 2X. The output from openRTSP is 22Mbps when analyzed using TSreader. I got the same 22Mbps results using an "unmodified version 0.19" live555 server in conjunction with the "-z 2" scale parameter of openRTSP.exe. The second test used Wireshark to analyze Ethernet traffic on a closed network between two PCs. Live555 version 0.19 serving the same 10Mbps stream to a PC running Wireshark and VLC as the RTSP client. In each case below, the scale was entered using stdin prior to stream open. My results are as follows: SCALE AVG Mbit/sec Time between 1st Packets AVG packets/sec AVG packet size IO Observation/time. and last packet 1X 10.429 66.989 sec 63795 952.322 1368.0 bytes Steady data rate. 1/2X 7.291 132.983 sec 102641 771.838 1180.0 bytes Bursty data rate. 2X 21.972 34.235 sec 79573 2324.345 1181.0 bytes Bursty data rate. 4X 22.065 17.772 sec 41483 2334.223 1181.0 bytes Bursty data rate. 8X 21.881 9.266 sec 21447 2314.648 1181.0 bytes Bursty data rate. 64X 22.207 2.212 sec 5195 2348.889 1181.0 bytes Bursty data rate. >From these results, it appears that there is either a naturally occurring maximum data rate of around 22Mbps in my particular setup or there may be some programmed maximum that is a function of the source data rate. In any case, some help in understanding these results or some help in finding a potential solution to clamping the maximum data rate would be much appreciated. Best regards, Marc Moody _______________________________________________ live-devel mailing list live-devel@lists.live555.com http://lists.live555.com/mailman/listinfo/live-devel
