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authorvan <vanj.hb@gmail.com>2008-06-12 08:12:18 +0000
committervan <vanj.hb@gmail.com>2008-06-12 08:12:18 +0000
commit60376035d60c6a40354ea1761cdcb18c7904bbc5 (patch)
tree3824dbe7a5c63220fc0ff93a15aaa7cb38dcc3a3 /libhb/decavcodec.c
parent1d07b9dea5174df9a3ed2a0a1ba5b21322b50b07 (diff)
- put the "find a usable frame rate" logic in the place that actually computes decoder frame durations rather than just in the bitstream info routine.
- start adding some comments describing how this horrible mess works. git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@1506 b64f7644-9d1e-0410-96f1-a4d463321fa5
Diffstat (limited to 'libhb/decavcodec.c')
-rw-r--r--libhb/decavcodec.c80
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 (?!)