Changes between Version 42 and Version 43 of DirectShow

Timestamp:

Jul 1, 2015, 4:53:11 PM (11 years ago)

Author:

Roger Pack

Comment:

mention the async.

DirectShow

@@ -100 +100 @@
 
 
-Also this note [http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=3&t=27 that] the input string is in the format video=<video device name>:audio=<audio device name>. It is possible to have two separate inputs (like -f dshow -i audio=foo -f dshow -i video=bar) though some limited tests had shown a difference in  synchronism between the two options.
+Also this note [http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=3&t=27 that] the input string is in the format video=<video device name>:audio=<audio device name>. It is possible to have two separate inputs (like -f dshow -i audio=foo -f dshow -i video=bar) though some limited tests had shown a difference in  synchronism between the two options at times.  Possibly you can overcome it using the "-copy_ts" flag.  The reason this works is that each "input" is assumed to start "at its first input time" and FFmpeg, by default, basically normalizes it "from its first input" as meaning "0.0 seconds."  Because ffmpeg is using two different dshow inputs, it basically starts one up, then starts up the second *after* so it might start sending in packets a fraction of a second later, and FFmpeg happily treats its "later starting" timestamps as also 0.0 so mixing them doesn't work well if they start off set.  So if you use -copy_ts then it will start them with "relative to machine start time" timestamps which should be able to mix accurately in theory.  Ping me if you want it fixed to come more than one audio and one video in an input and thus not need these work arounds rogerdpack@gmail.com
 
 Also note that you can only at most have 2 streams at once (one audio and one video, like -i video=XX:audio=YY).  Ask if you want this improved.  You can have multiples one after the other, however, like -f dshow -i video=XX:audio=ZZ -f dshow -i video=ZZ:audio=QQ etc.  FFmpeg can also "merge/combine" audio inputs using its amix filter.
 
-See the [http://ffmpeg.org/ffmpeg-devices.html#dshow FFmpeg dshow input device documentation] for a list of more dshow options you can specify. For instance you can decrease latency on audio devices, or specify a video by "index" if two have the same name, etc.
+See the [http://ffmpeg.org/ffmpeg-devices.html#dshow FFmpeg dshow input device documentation] for a list of more dshow options you can specify. For instance you can decrease latency on audio devices, or specify a video by "index" if two have the same name, etc. etc.
 
 === Specifying input framerate ===