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Code Issues Releases Activity

libzvbi-teletextdec: split dvb packet to slices

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Instead of using the demux function of libzvbi to split the packet to slices
(vbi lines), lets do it ourselves.

- eliminates the 1 frame delay between page input and output
- handles non-ascending line numbers more gracefully
- enables us to return error codes on some invalid packets instead of silently
  ignoring them

Signed-off-by: Marton Balint <cus@passwd.hu>
This commit is contained in:
Marton Balint 2014-03-01 02:10:15 +01:00
parent ae017c2632
commit 085ca7dcdb
1 changed files with 54 additions and 32 deletions
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86
libavcodec/libzvbi-teletextdec.c
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@ -37,6 +37,7 @@
#define MAX_BUFFERED_PAGES 25
#define BITMAP_CHAR_WIDTH 12
#define BITMAP_CHAR_HEIGHT 10
#define MAX_SLICES 64
typedef struct TeletextPage
{
@ -65,11 +66,10 @@ typedef struct TeletextContext
int handler_ret;
vbi_decoder * vbi;
vbi_dvb_demux * dx;
#ifdef DEBUG
vbi_export * ex;
#endif
vbi_sliced sliced[64];
vbi_sliced sliced[MAX_SLICES];
} TeletextContext;
static int chop_spaces_utf8(const unsigned char* t, int len)
@ -358,15 +358,46 @@ static void handler(vbi_event *ev, void *user_data)
vbi_unref_page(&page);
}
static inline int data_identifier_is_teletext(int data_identifier) {
/* See EN 301 775 section 4.4.2. */
return (data_identifier >= 0x10 && data_identifier <= 0x1F ||
data_identifier >= 0x99 && data_identifier <= 0x9B);
}
static int slice_to_vbi_lines(TeletextContext *ctx, uint8_t* buf, int size)
{
int lines = 0;
while (size >= 2 && lines < MAX_SLICES) {
int data_unit_id = buf[0];
int data_unit_length = buf[1];
if (data_unit_length + 2 > size)
return AVERROR_INVALIDDATA;
if (data_unit_id == 0x02 || data_unit_id == 0x03) {
if (data_unit_length != 0x2c)
return AVERROR_INVALIDDATA;
else {
int line_offset = buf[2] & 0x1f;
int field_parity = buf[2] & 0x20;
int i;
ctx->sliced[lines].id = VBI_SLICED_TELETEXT_B;
ctx->sliced[lines].line = (line_offset > 0 ? (line_offset + (field_parity ? 0 : 313)) : 0);
for (i = 0; i < 42; i++)
ctx->sliced[lines].data[i] = vbi_rev8(buf[4 + i]);
lines++;
}
}
size -= data_unit_length + 2;
buf += data_unit_length + 2;
}
if (size)
av_log(ctx, AV_LOG_WARNING, "%d bytes remained after slicing data\n", size);
return lines;
}
static int teletext_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *pkt)
{
TeletextContext *ctx = avctx->priv_data;
AVSubtitle *sub = data;
const uint8_t *buf = pkt->data;
int left = pkt->size;
uint8_t pesheader[45] = {0x00, 0x00, 0x01, 0xbd, 0x00, 0x00, 0x85, 0x80, 0x24, 0x21, 0x00, 0x01, 0x00, 0x01};
int pesheader_size = sizeof(pesheader);
const uint8_t *pesheader_buf = pesheader;
int ret = 0;
if (!ctx->vbi) {
@ -378,40 +409,34 @@ static int teletext_decode_frame(AVCodecContext *avctx, void *data, int *data_si
return AVERROR(ENOMEM);
}
}
if (!ctx->dx && (!(ctx->dx = vbi_dvb_pes_demux_new (/* callback */ NULL, NULL))))
return AVERROR(ENOMEM);
if (avctx->pkt_timebase.den && pkt->pts != AV_NOPTS_VALUE)
ctx->pts = av_rescale_q(pkt->pts, avctx->pkt_timebase, AV_TIME_BASE_Q);
if (left) {
if (pkt->size) {
int lines;
const int full_pes_size = pkt->size + 45; /* PES header is 45 bytes */
// We allow unreasonably big packets, even if the standard only allows a max size of 1472
if ((pesheader_size + left) < 184 || (pesheader_size + left) > 65504 || (pesheader_size + left) % 184 != 0)
if (full_pes_size < 184 || full_pes_size > 65504 || full_pes_size % 184 != 0)
return AVERROR_INVALIDDATA;
memset(pesheader + 14, 0xff, pesheader_size - 14);
AV_WB16(pesheader + 4, left + pesheader_size - 6);
/* PTS is deliberately left as 0 in the PES header, otherwise libzvbi uses
* it to detect dropped frames. Unforunatey the guessed packet PTS values
* (see mpegts demuxer) are not accurate enough to pass that test. */
vbi_dvb_demux_cor(ctx->dx, ctx->sliced, 64, NULL, &pesheader_buf, &pesheader_size);
ctx->handler_ret = pkt->size;
while (left > 0) {
int64_t pts = 0;
unsigned int lines = vbi_dvb_demux_cor(ctx->dx, ctx->sliced, 64, &pts, &buf, &left);
av_dlog(avctx, "ctx=%p buf_size=%d left=%u lines=%u pts=%f pkt_pts=%f\n",
ctx, pkt->size, left, lines, (double)pts/90000.0, (double)pkt->pts/90000.0);
if (data_identifier_is_teletext(*pkt->data)) {
if ((lines = slice_to_vbi_lines(ctx, pkt->data + 1, pkt->size - 1)) < 0)
return lines;
av_dlog(avctx, "ctx=%p buf_size=%d lines=%u pkt_pts=%7.3f\n",
ctx, pkt->size, lines, (double)pkt->pts/90000.0);
if (lines > 0) {
#ifdef DEBUGx
#ifdef DEBUG
int i;
for(i=0; i<lines; ++i)
av_log(avctx, AV_LOG_DEBUG,
"lines=%d id=%x\n", i, ctx->sliced[i].id);
av_log(avctx, AV_LOG_DEBUG, "line numbers:");
for(i = 0; i < lines; i++)
av_log(avctx, AV_LOG_DEBUG, " %d", ctx->sliced[i].line);
av_log(avctx, AV_LOG_DEBUG, "\n");
#endif
vbi_decode(ctx->vbi, ctx->sliced, lines, (double)pts/90000.0);
vbi_decode(ctx->vbi, ctx->sliced, lines, 0.0);
ctx->lines_processed += lines;
}
}
@ -474,7 +499,6 @@ static int teletext_init_decoder(AVCodecContext *avctx)
avctx->height = 25 * BITMAP_CHAR_HEIGHT;
}
ctx->dx = NULL;
ctx->vbi = NULL;
ctx->pts = AV_NOPTS_VALUE;
@ -497,9 +521,7 @@ static int teletext_close_decoder(AVCodecContext *avctx)
subtitle_rect_free(&ctx->pages[--ctx->nb_pages].sub_rect);
av_freep(&ctx->pages);
vbi_dvb_demux_delete(ctx->dx);
vbi_decoder_delete(ctx->vbi);
ctx->dx = NULL;
ctx->vbi = NULL;
ctx->pts = AV_NOPTS_VALUE;
return 0;