No subject

[bogus at does.not.exist.com]

enum AVDiscard{
    /* We leave some space between them for extensions (drop some
     * keyframes for intra-only or drop just some bidir frames). */
    AVDISCARD_NONE   =-16, ///< discard nothing
    AVDISCARD_DEFAULT=  0, ///< discard useless packets like 0 size packets in avi
    AVDISCARD_NONREF =  8, ///< discard all non reference
    AVDISCARD_BIDIR  = 16, ///< discard all bidirectional frames
    AVDISCARD_NONKEY = 32, ///< discard all frames except keyframes
    AVDISCARD_ALL    = 48, ///< discard all
};

So AVStream.discard seems to control which packets should be
discarded, rather than to select the stream to playback, and still I
have no idea how/if it is possible to set it via commandline.

So maybe, the sentence:
the streams to receive are chosen according to the @var{discard} field in AVStream

should be replaced by
the packets to discard are chosen according to the @var{discard} field in AVStream

That is, I can understand that it is possible to select one stream
with a particular bitrate from a multi-bitrate streams set, but I
still cannot understand what's the role of "discard" in this game.

If this is something related to options only settable programmatically
I suppose we can simply "discard" them in the docs (but mentioning it
in a more explicit way would be nicer).

[...]

Rest of the patch looks good to me, regards.
-- 
FFmpeg = Fundamentalist and Freak Most Portentous Evanescent Ghost