1Capsnego patterns 2----------------- 3 4 5 6 7src negotiation recovery 8------------------------ 9 10common pipelines like 11 12 filesrc -> mad -> osssink 13 14perform negotiation strictly left to right. At some point during 15iterate, mad will know the caps of the media stream and will need 16to inform osssink of this before pushing out a buffer. 17mad only has one set of fixed caps. 18 191) try_set_caps 20 21 mad does a try_set_caps with the caps if all goes well, osssink 22 accepts and negotiation succeeds. 23 24 if the try_set_caps function fails, the application should have 25 a change to recover. 26 27 - mad therefore calls gst_pad_caps_error_try_recover, this will 28 emit a signal on the pad that the app can catch. One of the 29 signal arguments will contain a list of possible caps. 30 31 - the app can use the allowed caps to find another element that 32 is compatible with the caps and the peer element caps. 33 34 - the app will connect the new element with mad, negotiation 35 will happen again, the link will fail or succeed, if it fails, 36 thr app knows because the link function returns FALSE. 37 38 - if the link succeeds, pad caps are set and the try_recover 39 function returns TRUE, mad then knows the issue was resolved 40 and can continue. It will have received the final caps in its 41 srclink function. 42 43 - if no signal handler is connected to the caps_nego_failure signal 44 the issue will remain unresolved and a big debug warning is 45 printed on the console to debug the issue. mad will get a 46 return value of FALSE and may stop. 47 48 49