diff options
Diffstat (limited to 'libhb/decavcodec.c')
| -rw-r--r-- | libhb/decavcodec.c | 80 |
1 files changed, 77 insertions, 3 deletions
diff --git a/libhb/decavcodec.c b/libhb/decavcodec.c index 10a750142..c49dcc79c 100644 --- a/libhb/decavcodec.c +++ b/libhb/decavcodec.c @@ -4,6 +4,61 @@ Homepage: <http://handbrake.fr/>. It may be used under the terms of the GNU General Public License. */ +/* This module is Handbrake's interface to the ffmpeg decoder library + (libavcodec & small parts of libavformat). It contains four Handbrake + "work objects": + + decavcodec connects HB to an ffmpeg audio decoder + decavcodecv connects HB to an ffmpeg video decoder + + (Two different routines are needed because the ffmpeg library + has different decoder calling conventions for audio & video. + The audio decoder should have had its name changed to "decavcodeca" + but I got lazy.) These work objects are self-contained & follow all + of HB's conventions for a decoder module. They can be used like + any other HB decoder (deca52, decmpeg2, etc.). + + decavcodecai "internal" (incestuous?) version of decavcodec + decavcodecvi "internal" (incestuous?) version of decavcodecv + + These routine are functionally equivalent to the routines above but + can only be used by the ffmpeg-based stream reader in libhb/stream.c. + The reason they exist is because the ffmpeg library leaves some of + the information needed by the decoder in the AVStream (the data + structure used by the stream reader) and we need to retrieve it + to successfully decode frames. But in HB the reader and decoder + modules are in completely separate threads and nothing goes between + them but hb_buffers containing frames to be decoded. I.e., there's + no easy way for the ffmpeg stream reader to pass a pointer to its + AVStream over to the ffmpeg video or audio decoder. So the *i work + objects use a private back door to the stream reader to get access + to the AVStream (routines hb_ffmpeg_avstream and hb_ffmpeg_context) + and the codec_param passed to these work objects is the key to this + back door (it's basically an index that allows the correct AVStream + to be retrieved). + + The normal & *i objects share a lot of code (the basic frame decoding + and bitstream info code is factored out into subroutines that can be + called by either) but the top level routines of the *i objects + (decavcodecviWork, decavcodecviInfo, etc.) are different because: + 1) they *have* to use the AVCodecContext that's contained in the + reader's AVStream rather than just allocating & using their own, + 2) the Info routines have access to stuff kept in the AVStream in addition + to stuff kept in the AVCodecContext. This shouldn't be necessary but + crucial information like video frame rate that should be in the + AVCodecContext is either missing or wrong in the version of ffmpeg + we're currently using. + + A consequence of the above is that the non-i work objects *can't* use + information from the AVStream because there isn't one - they get their + data from either the dvd reader or the mpeg reader, not the ffmpeg stream + reader. That means that they have to make up for deficiencies in the + AVCodecContext info by using stuff kept in the HB "title" struct. It + also means that ffmpeg codecs that randomly scatter state needed by + the decoder across both the AVCodecContext & the AVStream (e.g., the + VC1 decoder) can't easily be used by the HB mpeg stream reader. + */ + #include "hb.h" #include "libavcodec/avcodec.h" @@ -542,14 +597,33 @@ static void init_ffmpeg_context( hb_work_object_t *w ) avcodec_open( pv->context, codec ); } // set up our best guess at the frame duration. - // the frame rate in the codec seems to be bogus but it's ok in the stream. + // the frame rate in the codec is usually bogus but it's sometimes + // ok in the stream. AVStream *st = hb_ffmpeg_avstream( w->codec_param ); - AVRational tb = st->time_base; - if ( st->r_frame_rate.den && st->r_frame_rate.num ) + AVRational tb; + // XXX because the time bases are so screwed up, we only take values + // in the range 8fps - 64fps. + if ( st->time_base.num * 64 > st->time_base.den && + st->time_base.den > st->time_base.num * 8 ) + { + tb = st->time_base; + } + else if ( st->codec->time_base.num * 64 > st->codec->time_base.den && + st->codec->time_base.den > st->codec->time_base.num * 8 ) + { + tb = st->codec->time_base; + } + else if ( st->r_frame_rate.den * 64 > st->r_frame_rate.num && + st->r_frame_rate.num > st->r_frame_rate.den * 8 ) { tb.num = st->r_frame_rate.den; tb.den = st->r_frame_rate.num; } + else + { + tb.num = 1001; /*XXX*/ + tb.den = 30000; /*XXX*/ + } pv->duration = 90000. * tb.num / tb.den; // we have to wrap ffmpeg's get_buffer to be able to set the pts (?!) |