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Improve support for PGS subtitles.

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The previous implementation assumed that a new picture would always
supersede the previous picture. Similarly, presentation segments
were assumed to pertain to the most-recently-read picture.

However, each presentation segment may refer to 0 or more pictures
by their ID. Picture IDs may repeat, and a repeated picture ID
indicates that the old picture for that ID is no longer needed
and may be discarded.

The new implementation allocates a buffer with one slot for each
possible picture ID (the picture ID is a 16-bit field) and
properly decodes presentation segments so that all relevant
pictures are output upon encountering a display segment.

Given that most PGS streams are unlikely to use more than a small
fraction of the available picture IDs, it would probably be better
to use a more memory-efficient data structure. I'm lazy though, so
I leave this to a more motivated individual.

I've tested the code with MKV files in VLC (a recent revision from
their git repo) and with HandBrake (a version that I hacked up to
use ffmpeg's PGS subtitle decoder).

Review-by: Hendrik Leppkes <h.leppkes@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
David Mitchell 2012-01-19 07:31:01 -08:00 committed by Michael Niedermayer
parent cf7c7f13cd
commit d150a147da
2 changed files with 118 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Changelog
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@ -26,6 +26,7 @@ version next:
- ffprobe -show_program_version, -show_library_versions, -show_versions options
- rv34: frame-level multi-threading
- optimized iMDCT transform on x86 using SSE for for mpegaudiodec
- Improved PGS subtitle decoder
version 0.9:

198
libavcodec/pgssubdec.c
View File

@ -40,11 +40,16 @@ enum SegmentType {
DISPLAY_SEGMENT = 0x80,
};
typedef struct PGSSubPresentation {
typedef struct PGSSubPictureReference {
int x;
int y;
int id_number;
int object_number;
int picture_id;
} PGSSubPictureReference;
typedef struct PGSSubPresentation {
int id_number;
int object_count;
PGSSubPictureReference *objects;
} PGSSubPresentation;
typedef struct PGSSubPicture {
@ -58,22 +63,29 @@ typedef struct PGSSubPicture {
typedef struct PGSSubContext {
PGSSubPresentation presentation;
uint32_t clut[256];
PGSSubPicture picture;
PGSSubPicture pictures[UINT16_MAX];
} PGSSubContext;
static av_cold int init_decoder(AVCodecContext *avctx)
{
avctx->pix_fmt = PIX_FMT_PAL8;
avctx->pix_fmt = PIX_FMT_PAL8;
return 0;
}
static av_cold int close_decoder(AVCodecContext *avctx)
{
uint16_t picture;
PGSSubContext *ctx = avctx->priv_data;
av_freep(&ctx->picture.rle);
ctx->picture.rle_buffer_size = 0;
av_freep(&ctx->presentation.objects);
ctx->presentation.object_count = 0;
for (picture = 0; picture < UINT16_MAX; ++picture) {
av_freep(&ctx->pictures[picture].rle);
ctx->pictures[picture].rle_buffer_size = 0;
}
return 0;
}
@ -88,7 +100,7 @@ static av_cold int close_decoder(AVCodecContext *avctx)
* @param buf pointer to the RLE data to process
* @param buf_size size of the RLE data to process
*/
static int decode_rle(AVCodecContext *avctx, AVSubtitle *sub,
static int decode_rle(AVCodecContext *avctx, AVSubtitle *sub, int rect,
const uint8_t *buf, unsigned int buf_size)
{
const uint8_t *rle_bitmap_end;
@ -96,15 +108,15 @@ static int decode_rle(AVCodecContext *avctx, AVSubtitle *sub,
rle_bitmap_end = buf + buf_size;
sub->rects[0]->pict.data[0] = av_malloc(sub->rects[0]->w * sub->rects[0]->h);
sub->rects[rect]->pict.data[0] = av_malloc(sub->rects[rect]->w * sub->rects[rect]->h);
if (!sub->rects[0]->pict.data[0])
if (!sub->rects[rect]->pict.data[0])
return -1;
pixel_count = 0;
line_count = 0;
while (buf < rle_bitmap_end && line_count < sub->rects[0]->h) {
while (buf < rle_bitmap_end && line_count < sub->rects[rect]->h) {
uint8_t flags, color;
int run;
@ -119,27 +131,27 @@ static int decode_rle(AVCodecContext *avctx, AVSubtitle *sub,
color = flags & 0x80 ? bytestream_get_byte(&buf) : 0;
}
if (run > 0 && pixel_count + run <= sub->rects[0]->w * sub->rects[0]->h) {
memset(sub->rects[0]->pict.data[0] + pixel_count, color, run);
if (run > 0 && pixel_count + run <= sub->rects[rect]->w * sub->rects[rect]->h) {
memset(sub->rects[rect]->pict.data[0] + pixel_count, color, run);
pixel_count += run;
} else if (!run) {
/*
* New Line. Check if correct pixels decoded, if not display warning
* and adjust bitmap pointer to correct new line position.
*/
if (pixel_count % sub->rects[0]->w > 0)
if (pixel_count % sub->rects[rect]->w > 0)
av_log(avctx, AV_LOG_ERROR, "Decoded %d pixels, when line should be %d pixels\n",
pixel_count % sub->rects[0]->w, sub->rects[0]->w);
pixel_count % sub->rects[rect]->w, sub->rects[rect]->w);
line_count++;
}
}
if (pixel_count < sub->rects[0]->w * sub->rects[0]->h) {
if (pixel_count < sub->rects[rect]->w * sub->rects[rect]->h) {
av_log(avctx, AV_LOG_ERROR, "Insufficient RLE data for subtitle\n");
return -1;
}
av_dlog(avctx, "Pixel Count = %d, Area = %d\n", pixel_count, sub->rects[0]->w * sub->rects[0]->h);
av_dlog(avctx, "Pixel Count = %d, Area = %d\n", pixel_count, sub->rects[rect]->w * sub->rects[rect]->h);
return 0;
}
@ -162,25 +174,28 @@ static int parse_picture_segment(AVCodecContext *avctx,
uint8_t sequence_desc;
unsigned int rle_bitmap_len, width, height;
uint16_t picture_id;
if (buf_size <= 4)
return -1;
buf_size -= 4;
/* skip 3 unknown bytes: Object ID (2 bytes), Version Number */
buf += 3;
picture_id = bytestream_get_be16(&buf);
/* skip 1 unknown byte: Version Number */
buf++;
/* Read the Sequence Description to determine if start of RLE data or appended to previous RLE */
sequence_desc = bytestream_get_byte(&buf);
if (!(sequence_desc & 0x80)) {
/* Additional RLE data */
if (buf_size > ctx->picture.rle_remaining_len)
if (buf_size > ctx->pictures[picture_id].rle_remaining_len)
return -1;
memcpy(ctx->picture.rle + ctx->picture.rle_data_len, buf, buf_size);
ctx->picture.rle_data_len += buf_size;
ctx->picture.rle_remaining_len -= buf_size;
memcpy(ctx->pictures[picture_id].rle + ctx->pictures[picture_id].rle_data_len, buf, buf_size);
ctx->pictures[picture_id].rle_data_len += buf_size;
ctx->pictures[picture_id].rle_remaining_len -= buf_size;
return 0;
}
@ -202,17 +217,17 @@ static int parse_picture_segment(AVCodecContext *avctx,
return -1;
}
ctx->picture.w = width;
ctx->picture.h = height;
ctx->pictures[picture_id].w = width;
ctx->pictures[picture_id].h = height;
av_fast_malloc(&ctx->picture.rle, &ctx->picture.rle_buffer_size, rle_bitmap_len);
av_fast_malloc(&ctx->pictures[picture_id].rle, &ctx->pictures[picture_id].rle_buffer_size, rle_bitmap_len);
if (!ctx->picture.rle)
if (!ctx->pictures[picture_id].rle)
return -1;
memcpy(ctx->picture.rle, buf, buf_size);
ctx->picture.rle_data_len = buf_size;
ctx->picture.rle_remaining_len = rle_bitmap_len - buf_size;
memcpy(ctx->pictures[picture_id].rle, buf, buf_size);
ctx->pictures[picture_id].rle_data_len = buf_size;
ctx->pictures[picture_id].rle_remaining_len = rle_bitmap_len - buf_size;
return 0;
}
@ -275,11 +290,11 @@ static void parse_presentation_segment(AVCodecContext *avctx,
{
PGSSubContext *ctx = avctx->priv_data;
int x, y;
int w = bytestream_get_be16(&buf);
int h = bytestream_get_be16(&buf);
uint16_t object_index;
av_dlog(avctx, "Video Dimensions %dx%d\n",
w, h);
if (av_image_check_size(w, h, 0, avctx) >= 0)
@ -298,34 +313,48 @@ static void parse_presentation_segment(AVCodecContext *avctx,
*/
buf += 3;
ctx->presentation.object_number = bytestream_get_byte(&buf);
if (!ctx->presentation.object_number)
ctx->presentation.object_count = bytestream_get_byte(&buf);
if (!ctx->presentation.object_count)
return;
/*
* Skip 4 bytes of unknown:
* object_id_ref (2 bytes),
* window_id_ref,
* composition_flag (0x80 - object cropped, 0x40 - object forced)
*/
buf += 4;
x = bytestream_get_be16(&buf);
y = bytestream_get_be16(&buf);
/* TODO If cropping, cropping_x, cropping_y, cropping_width, cropping_height (all 2 bytes).*/
av_dlog(avctx, "Subtitle Placement x=%d, y=%d\n", x, y);
if (x > avctx->width || y > avctx->height) {
av_log(avctx, AV_LOG_ERROR, "Subtitle out of video bounds. x = %d, y = %d, video width = %d, video height = %d.\n",
x, y, avctx->width, avctx->height);
x = 0; y = 0;
/* Verify that enough bytes are remaining for all of the objects. */
buf_size -= 11;
if (buf_size < ctx->presentation.object_count * 8) {
ctx->presentation.object_count = 0;
return;
}
/* Fill in dimensions */
ctx->presentation.x = x;
ctx->presentation.y = y;
av_freep(&ctx->presentation.objects);
ctx->presentation.objects = av_malloc(sizeof(PGSSubPictureReference) * ctx->presentation.object_count);
if (!ctx->presentation.objects) {
ctx->presentation.object_count = 0;
return;
}
for (object_index = 0; object_index < ctx->presentation.object_count; ++object_index) {
PGSSubPictureReference *reference = &ctx->presentation.objects[object_index];
reference->picture_id = bytestream_get_be16(&buf);
/*
* Skip 2 bytes of unknown:
* window_id_ref,
* composition_flag (0x80 - object cropped, 0x40 - object forced)
*/
buf += 2;
reference->x = bytestream_get_be16(&buf);
reference->y = bytestream_get_be16(&buf);
/* TODO If cropping, cropping_x, cropping_y, cropping_width, cropping_height (all 2 bytes).*/
av_dlog(avctx, "Subtitle Placement ID=%d, x=%d, y=%d\n", reference->picture_id, reference->x, reference->y);
if (reference->x > avctx->width || reference->y > avctx->height) {
av_log(avctx, AV_LOG_ERROR, "Subtitle out of video bounds. x = %d, y = %d, video width = %d, video height = %d.\n",
reference->x, reference->y, avctx->width, avctx->height);
reference->x = 0;
reference->y = 0;
}
}
}
/**
@ -349,45 +378,52 @@ static int display_end_segment(AVCodecContext *avctx, void *data,
AVSubtitle *sub = data;
PGSSubContext *ctx = avctx->priv_data;
uint16_t rect;
/*
* The end display time is a timeout value and is only reached
* if the next subtitle is later then timeout or subtitle has
* if the next subtitle is later than timeout or subtitle has
* not been cleared by a subsequent empty display command.
*/
// Blank if last object_number was 0.
// Note that this may be wrong for more complex subtitles.
if (!ctx->presentation.object_number)
memset(sub, 0, sizeof(*sub));
// Blank if last object_count was 0.
if (!ctx->presentation.object_count)
return 1;
sub->start_display_time = 0;
sub->end_display_time = 20000;
sub->format = 0;
sub->rects = av_mallocz(sizeof(*sub->rects));
sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
sub->num_rects = 1;
sub->num_rects = ctx->presentation.object_count;
sub->rects = av_mallocz(sizeof(*sub->rects) * sub->num_rects);
sub->rects[0]->x = ctx->presentation.x;
sub->rects[0]->y = ctx->presentation.y;
sub->rects[0]->w = ctx->picture.w;
sub->rects[0]->h = ctx->picture.h;
sub->rects[0]->type = SUBTITLE_BITMAP;
for (rect = 0; rect < sub->num_rects; ++rect) {
uint16_t picture_id = ctx->presentation.objects[rect].picture_id;
sub->rects[rect] = av_mallocz(sizeof(*sub->rects[rect]));
sub->rects[rect]->x = ctx->presentation.objects[rect].x;
sub->rects[rect]->y = ctx->presentation.objects[rect].y;
sub->rects[rect]->w = ctx->pictures[picture_id].w;
sub->rects[rect]->h = ctx->pictures[picture_id].h;
sub->rects[rect]->type = SUBTITLE_BITMAP;
/* Process bitmap */
sub->rects[0]->pict.linesize[0] = ctx->picture.w;
/* Process bitmap */
sub->rects[rect]->pict.linesize[0] = ctx->pictures[picture_id].w;
if (ctx->pictures[picture_id].rle) {
if (ctx->pictures[picture_id].rle_remaining_len)
av_log(avctx, AV_LOG_ERROR, "RLE data length %u is %u bytes shorter than expected\n",
ctx->pictures[picture_id].rle_data_len, ctx->pictures[picture_id].rle_remaining_len);
if (decode_rle(avctx, sub, rect, ctx->pictures[picture_id].rle, ctx->pictures[picture_id].rle_data_len) < 0)
return 0;
}
if (ctx->picture.rle) {
if (ctx->picture.rle_remaining_len)
av_log(avctx, AV_LOG_ERROR, "RLE data length %u is %u bytes shorter than expected\n",
ctx->picture.rle_data_len, ctx->picture.rle_remaining_len);
if(decode_rle(avctx, sub, ctx->picture.rle, ctx->picture.rle_data_len) < 0)
return 0;
/* Allocate memory for colors */
sub->rects[rect]->nb_colors = 256;
sub->rects[rect]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
memcpy(sub->rects[rect]->pict.data[1], ctx->clut, sub->rects[rect]->nb_colors * sizeof(uint32_t));
}
/* Allocate memory for colors */
sub->rects[0]->nb_colors = 256;
sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
memcpy(sub->rects[0]->pict.data[1], ctx->clut, sub->rects[0]->nb_colors * sizeof(uint32_t));
return 1;
}