read_packet reads content in chunks. Thus seek must be clamped to valid
chunk positions in the file, which in turn are relative to chapter start
positions.
So in read_header, scan for chapter headers once by skipping through the
content. Set stream time_base to bitrate in bytes/s, for easy timestamp to
position conversion.
Then in read_seek, find the chapter containing the seek position, calculate
the nearest chunk position, and reinit the read_seek state accordingly.
---
libavformat/aadec.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 72 insertions(+), 3 deletions(-)
diff --git a/libavformat/aadec.c b/libavformat/aadec.c
index d6b6c125da..2480781df0 100644
--- a/libavformat/aadec.c
+++ b/libavformat/aadec.c
@@ -35,6 +35,7 @@
#define MAX_TOC_ENTRIES 16
#define MAX_DICTIONARY_ENTRIES 128
#define TEA_BLOCK_SIZE 8
+#define CHAPTER_HEADER_SIZE 8
typedef struct AADemuxContext {
AVClass *class;
@@ -46,6 +47,7 @@ typedef struct AADemuxContext {
struct AVTEA *tea_ctx;
uint8_t file_key[16];
int64_t current_chapter_size;
+ int64_t content_start;
int64_t content_end;
} AADemuxContext;
@@ -70,7 +72,7 @@ static int aa_read_header(AVFormatContext *s)
uint32_t nkey, nval, toc_size, npairs, header_seed = 0, start;
char key[128], val[128], codec_name[64] = {0};
uint8_t output[24], dst[8], src[8];
- int64_t largest_size = -1, current_size = -1;
+ int64_t largest_size = -1, current_size = -1, chapter_pos;
struct toc_entry {
uint32_t offset;
uint32_t size;
@@ -172,19 +174,23 @@ static int aa_read_header(AVFormatContext *s)
if (!strcmp(codec_name, "mp332")) {
st->codecpar->codec_id = AV_CODEC_ID_MP3;
st->codecpar->sample_rate = 22050;
+ st->time_base = av_make_q(8, 32000);
st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
- st->start_time = 0;
} else if (!strcmp(codec_name, "acelp85")) {
st->codecpar->codec_id = AV_CODEC_ID_SIPR;
st->codecpar->block_align = 19;
st->codecpar->channels = 1;
st->codecpar->sample_rate = 8500;
+ st->codecpar->bit_rate = 8500;
+ st->time_base = av_make_q(8, 8500);
st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
} else if (!strcmp(codec_name, "acelp16")) {
st->codecpar->codec_id = AV_CODEC_ID_SIPR;
st->codecpar->block_align = 20;
st->codecpar->channels = 1;
st->codecpar->sample_rate = 16000;
+ st->codecpar->bit_rate = 16000;
+ st->time_base = av_make_q(8, 16000);
st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
}
@@ -198,7 +204,30 @@ static int aa_read_header(AVFormatContext *s)
}
start = TOC[largest_idx].offset;
avio_seek(pb, start, SEEK_SET);
+
+ // extract chapter positions. since all formats have constant bit rate,
use it
+ // as time base in bytes/s, for easy stream position <-> timestamp
conversion
+ st->start_time = 0;
+ c->content_start = start;
c->content_end = start + largest_size;
+
+ while ((chapter_pos = avio_tell(pb)) >= 0 && chapter_pos < c->content_end)
{
+ int chapter_idx, chapter_size;
+ chapter_idx = s->nb_chapters;
+ chapter_pos -= start + CHAPTER_HEADER_SIZE * chapter_idx;
+ chapter_size = avio_rb32(pb);
+ if (chapter_size == 0) break;
+ avio_skip(pb, 4);
+ avio_skip(pb, chapter_size);
+ if (!avpriv_new_chapter(s, chapter_idx, st->time_base,
+ chapter_pos, chapter_pos + chapter_size, NULL))
+ return AVERROR(ENOMEM);
+ }
+
+ st->duration = largest_size - CHAPTER_HEADER_SIZE * s->nb_chapters;
+
+ ff_update_cur_dts(s, st, 0);
+ avio_seek(pb, start, SEEK_SET);
c->current_chapter_size = 0;
return 0;
@@ -267,6 +296,45 @@ static int aa_read_packet(AVFormatContext *s, AVPacket
*pkt)
return 0;
}
+static int aa_read_seek(AVFormatContext *s,
+ int stream_index, int64_t timestamp, int flags)
+{
+ AADemuxContext *c = s->priv_data;
+ AVChapter *ch;
+ int64_t chapter_pos, chapter_start;
+ int chapter_idx = 0;
+
+ // find chapter containing seek timestamp
+ if (timestamp < 0)
+ timestamp = 0;
+
+ while (chapter_idx < s->nb_chapters && timestamp >=
s->chapters[chapter_idx]->end) {
+ ++chapter_idx;
+ }
+
+ if (chapter_idx >= s->nb_chapters) {
+ chapter_idx = s->nb_chapters - 1;
+ if (chapter_idx < 0) return -1; // there is no chapter.
+ timestamp = s->chapters[chapter_idx]->end;
+ }
+
+ ch = s->chapters[chapter_idx];
+
+ // sync by clamping timestamp to nearest valid block position in its
chapter
+ chapter_pos = (timestamp - ch->start) / c->codec_second_size *
c->codec_second_size;
+ chapter_start = c->content_start + ch->start + CHAPTER_HEADER_SIZE * (1 +
chapter_idx);
+
+ avio_seek(s->pb, chapter_start + chapter_pos, SEEK_SET);
+ c->current_codec_second_size = c->codec_second_size;
+ c->current_chapter_size = ch->end - ch->start;
+ c->current_chapter_size -= chapter_pos;
+ c->chapter_idx = 1 + chapter_idx;
+
+ ff_update_cur_dts(s, s->streams[0], ch->start + chapter_pos);
+
+ return 1;
+}
+
static int aa_probe(AVProbeData *p)
{
uint8_t *buf = p->buf;
@@ -312,6 +380,7 @@ AVInputFormat ff_aa_demuxer = {
.read_probe = aa_probe,
.read_header = aa_read_header,
.read_packet = aa_read_packet,
+ .read_seek = aa_read_seek,
.read_close = aa_read_close,
- .flags = AVFMT_GENERIC_INDEX,
+ .flags = AVFMT_NO_BYTE_SEEK | AVFMT_NOGENSEARCH,
};
--
2.14.3 (Apple Git-98)
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