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Code Issues Releases Activity

avformat/dvdvideodec: reset the subdemuxer on discontinuity instead of flushing

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DVDs naturally consist of segmented MPEG-PS blobs within a VOB
(i.e. VOBs are not linear). NAV packs set the segment boundaries.
When switching between segments, discontinuities occur and thus
the subdemuxer needs to be reset. The current approach to manage
this is by invoking ff_read_frame_flush() on the subdemuxer context,
via a callback function which is invoked during the menu or dvdnav
block functions. The same subdemuxer context is used throughout
the demux, with a stretched PTS wrap bits value (64) + disabled
overflow correction, and then flushed on each segment. Eventually,
a play_end context variable is set to declare EOF.

However, this approach causes frame drops. The block read flushes the
demuxer before the frame read is complete, causing frames to drop
on discontinuity. The play_end signal likewise ends playback before
the frame read is complete, causing frames to drop at end of the title.
To compound the issue, the PTS wrap bits value of 64 is wrong;
the VOBU limit is actually 32 and the overflow correction should work.

Instead, EOF the MPEG-PS subdemuxer organically when each VOB segment
ends, and re-open it if needed with the offset after the full frame read
is complete. In doing so, correct the PTS wrap behavior to 32 bits and
remove the play_end/segment_started signals and callback pattern.

Note that the timestamps as reported by the NAV packets are known as
"PTMs", so the fields storing the time prior to adjustment are renamed
accordingly. This makes it more clear when we are offsetting the
NAV packet reported timestamps versus what we present as a demuxer.

Signed-off-by: Marth64 <marth64@proxyid.net>
This commit is contained in:
Marth64 2024-10-07 18:04:57 -05:00
parent 1964faa568
commit a1ae66c827
1 changed files with 75 additions and 64 deletions
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139
libavformat/dvdvideodec.c
View File

@ -56,7 +56,7 @@
#define DVDVIDEO_MAX_PS_SEARCH_BLOCKS 128
#define DVDVIDEO_BLOCK_SIZE 2048
#define DVDVIDEO_TIME_BASE_Q (AVRational) { 1, 90000 }
#define DVDVIDEO_PTS_WRAP_BITS 64 /* VOBUs use 32 (PES allows 33) */
#define DVDVIDEO_PTS_WRAP_BITS 32 /* VOBUs use 32 (PES allows 33) */
#define DVDVIDEO_LIBDVDX_LOG_BUFFER_SIZE 1024
#define PCI_START_BYTE 45 /* complement dvdread's DSI_START_BYTE */
@ -115,8 +115,9 @@ typedef struct DVDVideoPlaybackState {
int pgc_nb_pg_est; /* number of PGs as reported by IFOs */
int pgcn; /* ID of the PGC we are playing */
int pgn; /* ID of the PG we are in now */
int ptm_discont; /* signal that a PTM discontinuity occurred */
int64_t ptm_offset; /* PTM discontinuity offset (as NAV value) */
int ptt; /* ID of the chapter we are in now */
int64_t ts_offset; /* PTS discontinuity offset (ex. VOB change) */
uint32_t vobu_duration; /* duration of the current VOBU */
uint32_t vobu_e_ptm; /* end PTM of the current VOBU */
int vtsn; /* ID of the active VTS (video title set) */
@ -163,11 +164,11 @@ typedef struct DVDVideoDemuxContext {
/* playback control */
int64_t first_pts; /* the PTS of the first video keyframe */
int play_end; /* signal EOF to the parent demuxer */
DVDVideoPlaybackState play_state; /* the active playback state */
int play_started; /* signal that playback has started */
DVDVideoPlaybackState play_state; /* the active playback state */
int64_t pts_offset; /* PTS discontinuity offset (ex. VOB change) */
int seek_warned; /* signal that we warned about seeking limits */
int segment_started; /* signal that subdemuxer is on a segment */
int subdemux_reset; /* signal that subdemuxer should be reset */
} DVDVideoDemuxContext;
static void dvdvideo_libdvdread_log(void *opaque, dvd_logger_level_t level,
@ -390,8 +391,7 @@ static int dvdvideo_menu_open(AVFormatContext *s, DVDVideoPlaybackState *state)
}
static int dvdvideo_menu_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState *state,
uint8_t *buf, int buf_size, int *p_is_nav_packet,
void (*flush_cb)(AVFormatContext *s))
uint8_t *buf, int buf_size, int *p_is_nav_packet)
{
int64_t blocks_read = 0;
uint8_t read_buf[DVDVIDEO_BLOCK_SIZE] = {0};
@ -399,6 +399,7 @@ static int dvdvideo_menu_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
dsi_t dsi = (dsi_t) {0};
(*p_is_nav_packet) = 0;
state->ptm_discont = 0;
if (buf_size != DVDVIDEO_BLOCK_SIZE) {
av_log(s, AV_LOG_ERROR, "Invalid buffer size (expected=%d actual=%d)\n",
@ -465,10 +466,8 @@ static int dvdvideo_menu_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
if (state->in_pgc) {
if (state->vobu_e_ptm != pci.pci_gi.vobu_s_ptm) {
if (flush_cb)
flush_cb(s);
state->ts_offset += state->vobu_e_ptm - pci.pci_gi.vobu_s_ptm;
state->ptm_discont = 1;
state->ptm_offset += state->vobu_e_ptm - pci.pci_gi.vobu_s_ptm;
}
} else {
state->in_pgc = 1;
@ -479,9 +478,10 @@ static int dvdvideo_menu_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
state->vobu_duration = pci.pci_gi.vobu_e_ptm - pci.pci_gi.vobu_s_ptm;
av_log(s, AV_LOG_DEBUG, "NAV packet: sector=%d "
"vobu_s_ptm=%d vobu_e_ptm=%d ts_offset=%" PRId64 "\n",
"vobu_s_ptm=%d vobu_e_ptm=%d ptm_offset=%" PRId64 "\n",
dsi.dsi_gi.nv_pck_lbn,
pci.pci_gi.vobu_s_ptm, pci.pci_gi.vobu_e_ptm, state->ts_offset);
pci.pci_gi.vobu_s_ptm, pci.pci_gi.vobu_e_ptm, state->ptm_offset);
(*p_is_nav_packet) = 1;
@ -615,8 +615,7 @@ end_dvdnav_error:
}
static int dvdvideo_play_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState *state,
uint8_t *buf, int buf_size, int *p_is_nav_packet,
void (*flush_cb)(AVFormatContext *s))
uint8_t *buf, int buf_size, int *p_is_nav_packet)
{
DVDVideoDemuxContext *c = s->priv_data;
@ -631,6 +630,7 @@ static int dvdvideo_play_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
dsi_t *e_dsi;
(*p_is_nav_packet) = 0;
state->ptm_discont = 0;
if (buf_size != DVDVIDEO_BLOCK_SIZE) {
av_log(s, AV_LOG_ERROR, "Invalid buffer size (expected=%d actual=%d)\n",
@ -776,10 +776,8 @@ static int dvdvideo_play_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
state->in_ps = 1;
} else {
if (state->vobu_e_ptm != e_pci->pci_gi.vobu_s_ptm) {
if (flush_cb)
flush_cb(s);
state->ts_offset += state->vobu_e_ptm - e_pci->pci_gi.vobu_s_ptm;
state->ptm_discont = 1;
state->ptm_offset += state->vobu_e_ptm - e_pci->pci_gi.vobu_s_ptm;
}
}
@ -938,11 +936,9 @@ static int dvdvideo_chapters_setup_preindex(AVFormatContext *s)
while (!(interrupt = ff_check_interrupt(&s->interrupt_callback))) {
if (c->opt_menu)
ret = dvdvideo_menu_next_ps_block(s, &state, nav_buf, DVDVIDEO_BLOCK_SIZE, &is_nav_packet,
NULL);
ret = dvdvideo_menu_next_ps_block(s, &state, nav_buf, DVDVIDEO_BLOCK_SIZE, &is_nav_packet);
else
ret = dvdvideo_play_next_ps_block(s, &state, nav_buf, DVDVIDEO_BLOCK_SIZE, &is_nav_packet,
NULL);
ret = dvdvideo_play_next_ps_block(s, &state, nav_buf, DVDVIDEO_BLOCK_SIZE, &is_nav_packet);
if (ret < 0 && ret != AVERROR_EOF)
goto end_close;
@ -1444,19 +1440,6 @@ static int dvdvideo_subp_stream_add_all(AVFormatContext *s)
return 0;
}
static void dvdvideo_subdemux_flush(AVFormatContext *s)
{
DVDVideoDemuxContext *c = s->priv_data;
if (!c->segment_started)
return;
av_log(s, AV_LOG_DEBUG, "flushing sub-demuxer\n");
avio_flush(&c->mpeg_pb.pub);
ff_read_frame_flush(c->mpeg_ctx);
c->segment_started = 0;
}
static int dvdvideo_subdemux_read_data(void *opaque, uint8_t *buf, int buf_size)
{
AVFormatContext *s = opaque;
@ -1465,25 +1448,32 @@ static int dvdvideo_subdemux_read_data(void *opaque, uint8_t *buf, int buf_size)
int ret;
int is_nav_packet;
if (c->play_end)
return AVERROR_EOF;
if (c->opt_menu)
ret = dvdvideo_menu_next_ps_block(s, &c->play_state, buf, buf_size, &is_nav_packet,
dvdvideo_subdemux_flush);
ret = dvdvideo_menu_next_ps_block(s, &c->play_state, buf, buf_size, &is_nav_packet);
else
ret = dvdvideo_play_next_ps_block(s, &c->play_state, buf, buf_size, &is_nav_packet,
dvdvideo_subdemux_flush);
ret = dvdvideo_play_next_ps_block(s, &c->play_state, buf, buf_size, &is_nav_packet);
if (ret == AVERROR_EOF) {
c->mpeg_pb.pub.eof_reached = 1;
c->play_end = 1;
if (ret < 0)
goto subdemux_eof;
return AVERROR_EOF;
if (is_nav_packet) {
if (c->play_state.ptm_discont) {
c->subdemux_reset = 1;
ret = AVERROR_EOF;
goto subdemux_eof;
}
return FFERROR_REDO;
}
if (ret == 0 && is_nav_packet)
return FFERROR_REDO;
return ret;
subdemux_eof:
c->mpeg_pb.pub.eof_reached = 1;
c->mpeg_pb.pub.error = ret;
c->mpeg_pb.pub.read_packet = NULL;
c->mpeg_pb.pub.buf_end = c->mpeg_pb.pub.buf_ptr = c->mpeg_pb.pub.buffer;
return ret;
}
@ -1525,12 +1515,24 @@ static int dvdvideo_subdemux_open(AVFormatContext *s)
c->mpeg_ctx->max_analyze_duration = 0;
c->mpeg_ctx->interrupt_callback = s->interrupt_callback;
c->mpeg_ctx->pb = &c->mpeg_pb.pub;
c->mpeg_ctx->correct_ts_overflow = 0;
c->mpeg_ctx->io_open = NULL;
return avformat_open_input(&c->mpeg_ctx, "", &ff_mpegps_demuxer.p, NULL);
}
static int dvdvideo_subdemux_reset(AVFormatContext *s)
{
int ret;
av_log(s, AV_LOG_VERBOSE, "Resetting sub-demuxer\n");
dvdvideo_subdemux_close(s);
if ((ret = dvdvideo_subdemux_open(s)) < 0)
return ret;
return 0;
}
static int dvdvideo_read_header(AVFormatContext *s)
{
DVDVideoDemuxContext *c = s->priv_data;
@ -1619,16 +1621,20 @@ static int dvdvideo_read_packet(AVFormatContext *s, AVPacket *pkt)
int st_mapped = 0;
AVStream *st_subdemux;
if (c->play_end)
return AVERROR_EOF;
ret = av_read_frame(c->mpeg_ctx, pkt);
if (ret < 0) {
if (c->subdemux_reset && ret == AVERROR_EOF) {
c->subdemux_reset = 0;
c->pts_offset = c->play_state.ptm_offset;
if ((ret = dvdvideo_subdemux_reset(s)) < 0)
return ret;
return FFERROR_REDO;
}
if (ret < 0)
return ret;
if (!c->segment_started)
c->segment_started = 1;
}
st_subdemux = c->mpeg_ctx->streams[pkt->stream_index];
is_key = pkt->flags & AV_PKT_FLAG_KEY;
@ -1656,8 +1662,8 @@ static int dvdvideo_read_packet(AVFormatContext *s, AVPacket *pkt)
c->play_started = 1;
}
pkt->pts += c->play_state.ts_offset - c->first_pts;
pkt->dts += c->play_state.ts_offset - c->first_pts;
pkt->pts += c->pts_offset - c->first_pts;
pkt->dts += c->pts_offset - c->first_pts;
if (pkt->pts < 0)
goto discard;
@ -1667,11 +1673,11 @@ static int dvdvideo_read_packet(AVFormatContext *s, AVPacket *pkt)
}
av_log(s, AV_LOG_TRACE, "st=%d pts=%" PRId64 " dts=%" PRId64 " "
"ts_offset=%" PRId64 " first_pts=%" PRId64 "\n",
"pts_offset=%" PRId64 " first_pts=%" PRId64 "\n",
pkt->stream_index, pkt->pts, pkt->dts,
c->play_state.ts_offset, c->first_pts);
c->pts_offset, c->first_pts);
return c->play_end ? AVERROR_EOF : 0;
return 0;
discard:
av_log(s, st_mapped ? AV_LOG_VERBOSE : AV_LOG_DEBUG,
@ -1700,6 +1706,7 @@ static int dvdvideo_close(AVFormatContext *s)
static int dvdvideo_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
{
DVDVideoDemuxContext *c = s->priv_data;
int ret;
int64_t new_nav_pts;
pci_t* new_nav_pci;
dsi_t* new_nav_dsi;
@ -1744,13 +1751,17 @@ static int dvdvideo_read_seek(AVFormatContext *s, int stream_index, int64_t time
c->play_state.in_ps = 0;
c->play_state.is_seeking = 1;
c->play_state.nav_pts = timestamp;
c->play_state.ts_offset = timestamp;
c->play_state.ptm_offset = timestamp;
c->play_state.ptm_discont = 0;
c->play_state.vobu_e_ptm = new_nav_pci->pci_gi.vobu_s_ptm;
c->first_pts = 0;
c->play_started = 0;
c->pts_offset = timestamp;
c->subdemux_reset = 0;
dvdvideo_subdemux_flush(s);
if ((ret = dvdvideo_subdemux_reset(s)) < 0)
return ret;
av_log(s, AV_LOG_DEBUG, "seeking: requested_nav_pts=%" PRId64 " new_nav_pts=%" PRId64 "\n",
timestamp, new_nav_pts);