@param graph the filter graph
@param target the filter(s) to which the command should be sent
"all" sends to all filters
otherwise it can be a filter or filter instance name
which will send the command to all matching filters.
@param cmd the command to send, for handling simplicity all commands must be alphanumeric only
@param arg the argument for the command
@param res a buffer with size res_size where the filter(s) can return a response.
@returns >=0 on success otherwise an error code.
AVERROR(ENOSYS) on unsupported commands
Send a command to one or more filter instances.
@param graph the filter graph @param target the filter(s) to which the command should be sent "all" sends to all filters otherwise it can be a filter or filter instance name which will send the command to all matching filters. @param cmd the command to send, for handling simplicity all commands must be alphanumeric only @param arg the argument for the command @param res a buffer with size res_size where the filter(s) can return a response.
@returns >=0 on success otherwise an error code. AVERROR(ENOSYS) on unsupported commands