Allocate an AVFormatContext for an output format.
avformat_free_context() can be used to free the context and
everything allocated by the framework within it.
@param *ctx is set to the created format context, or to NULL in
case of failure
@param oformat format to use for allocating the context, if NULL
format_name and filename are used instead
@param format_name the name of output format to use for allocating the
context, if NULL filename is used instead
@param filename the name of the filename to use for allocating the
context, may be NULL
@return >= 0 in case of success, a negative AVERROR code in case of
failure
Allocate an AVFormatContext for an output format. avformat_free_context() can be used to free the context and everything allocated by the framework within it.
@param *ctx is set to the created format context, or to NULL in case of failure @param oformat format to use for allocating the context, if NULL format_name and filename are used instead @param format_name the name of output format to use for allocating the context, if NULL filename is used instead @param filename the name of the filename to use for allocating the context, may be NULL @return >= 0 in case of success, a negative AVERROR code in case of failure