Hi Kumar, One thing more.
I am not sure whether the idea works on DM355. I thought the idea before while I worked on my DM6437, after several days thinking about it. I give up the idea. The reason is I have to switch processing between my h.264 encoder and the UDP/IP network processing, the switching will make H.264 encoder performance down a lot. The L1/L2 cache and internal memory overlay will occupy a lot of MIPS. I guess the situation is much better on DM355 since DM355 can let DSP doing encoding and transmit data by ARM. Regards Tonald DL 2008/7/31 Tonald DL <[EMAIL PROTECTED]> > Hi Kumar, > > The latency calculation is ideal if you are using UDP/IP in LAN. > > If you are using TCP/IP, extra delay for TCP/IP. If you are using > UDP/IP in WAN, streaming buffer for that have extra delay. > > To decrease the latency, you have to change the encoding/decoding > processing parally with the others. > > in encoder side, parral three parts: 1. image capture, 2. video > encoding, 3. network transmitting. > > the process like this: > > 1.while imager finished scaning the lines and transfer data to memory > by DMA, you will know how many line have been transfered to memory. > 2. now start to encoding the first a few lines of the images. > 3. while finished encoding the first lines, start transfer the data > immediately to receiver. > > The rest of the encoder side will like this: > > 1. Image encoder keep transfer data to memory by DMA, it should much > faster than encoder encoding data. > > 2. encoder will keep continue encoding with the tranferred image > lines. > > 3. every a few encoded block data network module will transmit to > receiver immediately > > Now the transmit latency become: > > First a few lines delay between imager and encoder + a few blocks > encoding delay + network transmitting > > total is much less than 100 ms. > > The decoder side also similar, don't wait the whole image data > transmitted complete, once received the a few block data, start to decoding. > > > finally, the whole system latency is much less. > > of course, it is the perfect condition. while in implementation, there > are a lot of thing make it difficult. > > You have to control the imager, modify the structure of encoder, > control the UDP/IP module, change the decoding processing structure of > decoder. and consider the UDP/IP lost package and arrive un-sequence. all > those things make the system complex and difficult to handle. > > It is possible but have to spend much more time on it. And finally, > maybe the network delay become the major latency. > > > Regards > Tonald DL > > > > > > > > > > > > > > 2008/7/30 Kumar Bala <[EMAIL PROTECTED]> > > Hi, >> Thats what I do now, I have a ping-pong buffering scheme. >> Jon, thanks for the information. Any idea what the best systems offer. >> Coz we want to beat that ! >> >> >> Albert Burbea wrote: >> > hi >> > actually it can be less (you can transmit while you encode and encode >> while >> > you get video) but it is VEEEEEEERY expensive. You have to buy heavy 3rd >> > party video codecs. >> > What is your problem? Maybe we can help you >> > Albert >> > >> > >> > On 7/30/08, Jon Povey <[EMAIL PROTECTED]> wrote: >> >>> From: [EMAIL PROTECTED] >> >>> [mailto:[EMAIL PROTECTED] >> >>> ] On Behalf Of Kumar Bala >> >>> Sent: 30 July 2008 11:12 >> >>> To: [email protected] >> >>> Subject: Measuring MPEG4 system latency on DM355 >> >>> >> >>> Hi, >> >>> I have an MPEG4 streaming system which capture live video at >> >>> 1280x720p using a HD camera module. Then it streams it over >> >>> to a PC running the client app such as VLC or mplayer. >> >>> >> >>> I believe I get a few hundred millisecond latency (about >> >>> 200-300 ms). We want to achieve a near analogue latency. >> >> Let's see, I'm not an expert but: >> >> >> >> 40ms to read in a frame (assuming 25fps) >> >> 30ms to encode >> >> Some amount of time to transmit the frame to receiver and have it >> >> decoded, then >> >> 40ms display time >> >> >> >> So I recon that's around 120ms minimum assuming instant transmit and >> >> decode, and no waiting for extra VSYNC on the receiver or anything.. >> >> >> >> -- >> >> Jon Povey, Design Engineer >> >> [EMAIL PROTECTED] | +44(0)1280 825983 >> >> >> >> >> >> Racelogic is a limited company registered in England. Registered number >> >> 2743719 . >> >> Registered Office Unit 10, Swan Business Centre, Osier Way, Buckingham, >> >> Bucks, MK18 1TB . >> >> The information contained in this electronic mail transmission is >> intended >> >> by Racelogic Ltd for the use of the named individual or entity to which >> it >> >> is directed and may contain information that is confidential or >> privileged. >> >> If you have received this electronic mail transmission in error, please >> >> delete it from your system without copying or forwarding it, and notify >> the >> >> sender of the error by reply email so that the sender's address records >> can >> >> be corrected. The views expressed by the sender of this communication >> do not >> >> necessarily represent those of Racelogic Ltd. Please note that >> Racelogic >> >> reserves the right to monitor e-mail communications passing through its >> >> network >> >> _______________________________________________ >> >> Davinci-linux-open-source mailing list >> >> [email protected] >> >> http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source >> >> >> > >> > >> > >> > >> > ------------------------------------------------------------------------ >> > >> > _______________________________________________ >> > Davinci-linux-open-source mailing list >> > [email protected] >> > http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source >> >> _______________________________________________ >> Davinci-linux-open-source mailing list >> [email protected] >> http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source >> > > > > -- > -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > Best Regards > Tonald DL > WebSite: http://dhcodec.quikstream.com.au/ > -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Best Regards Tonald DL WebSite: http://dhcodec.quikstream.com.au/
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