On May 15, 2013, at 09:36 , Bjoern Drabeck wrote: >> >> This is also what I noticed, when playing with probesize and analyzeduration >> trying to get the player to start more quickly (using mpegts (h264/aac) >> streams served through a memory buffer). >> >> This leads to the question why does a known stream need to get probed / >> analyzed at all? If all values are known, they could be set before, and >> decoding / playing should start right away, skipping the step of >> av_find_stream_info. Unfortunately so far I did not manage to get this to >> work, av_find_stream_info seems to set something which is required for >> decoding to work. >> >> I looked though the av_find_stream_info source code and did not find >> anything special happening there, or I did not recognize it. >> >> So, to reduce latency, what has to be set for a codec / context to allow to >> skip the time-consuming step of av_find_stream_info? > > > Just one thing I wanted to mention: > > When I am opening a file I call avformat_open_input, then after that I > call avformat_find_stream_info, and I am timing those calls: > > 'avformat_open_input': 9.7970 seconds > 'avformat_find_stream_info': 0.1080 seconds > > So for me the problem seems to be avformat_open_input. My testfiles > are all around that range, maybe +-2 sec
You mentioned that you read the files using http urls, so isn't there the download time included in the values you measure for avformat_open_input? In my case I fill a memory buffer first and then feed that to the avformat functions. Nevertheless I will time these two functions again. I always assumed that the time is lost in avformat_find_stream_info and not in avformat_open_input, but may be my assumption was wrong. > > As I mentioned before, changine probesize/analyzeduration from 5000000 > to 5000 doesn't seem show any visible effect (just ranging within the > usual fluctuations of the above timings) > > Is that what you experienced too? if I reduce probesize/analyzeduration it does not get faster, but at some point it fails to recognize the streams. At 100000 it does fail most of the time (mpegts h264/aac). Which is why I would love to configure all possible settings which can be set before these functions are called. _______________________________________________ Libav-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/libav-user
