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aadec: add chapters and seeking

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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 based on 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.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Karsten Otto 2018-07-08 11:46:26 +02:00 committed by Michael Niedermayer
parent 3bf39f2aef
commit 6cc6b619b9
1 changed files with 81 additions and 4 deletions
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85
libavformat/aadec.c
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@ -35,6 +35,8 @@
#define MAX_TOC_ENTRIES 16
#define MAX_DICTIONARY_ENTRIES 128
#define TEA_BLOCK_SIZE 8
#define CHAPTER_HEADER_SIZE 8
#define TIMEPREC 1000
typedef struct AADemuxContext {
AVClass *class;
@ -46,6 +48,7 @@ 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 +73,7 @@ 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;
@ -173,19 +176,23 @@ static int aa_read_header(AVFormatContext *s)
st->codecpar->codec_id = AV_CODEC_ID_MP3;
st->codecpar->sample_rate = 22050;
st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
st->start_time = 0;
avpriv_set_pts_info(st, 64, 8, 32000 * TIMEPREC);
} 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->need_parsing = AVSTREAM_PARSE_FULL_RAW;
avpriv_set_pts_info(st, 64, 8, 8500 * TIMEPREC);
} 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->need_parsing = AVSTREAM_PARSE_FULL_RAW;
avpriv_set_pts_info(st, 64, 8, 16000 * TIMEPREC);
}
/* determine, and jump to audio start offset */
@ -198,7 +205,28 @@ 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 = s->nb_chapters;
uint32_t chapter_size = avio_rb32(pb);
if (chapter_size == 0) break;
chapter_pos -= start + CHAPTER_HEADER_SIZE * chapter_idx;
avio_skip(pb, 4 + chapter_size);
if (!avpriv_new_chapter(s, chapter_idx, st->time_base,
chapter_pos * TIMEPREC, (chapter_pos + chapter_size) * TIMEPREC, NULL))
return AVERROR(ENOMEM);
}
st->duration = (largest_size - CHAPTER_HEADER_SIZE * s->nb_chapters) * TIMEPREC;
ff_update_cur_dts(s, st, 0);
avio_seek(pb, start, SEEK_SET);
c->current_chapter_size = 0;
return 0;
@ -215,9 +243,10 @@ static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
int written = 0;
int ret;
AADemuxContext *c = s->priv_data;
uint64_t pos = avio_tell(s->pb);
// are we at the end of the audio content?
if (avio_tell(s->pb) >= c->content_end) {
if (pos >= c->content_end) {
return AVERROR_EOF;
}
@ -230,6 +259,7 @@ static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
av_log(s, AV_LOG_DEBUG, "Chapter %d (%" PRId64 " bytes)\n", c->chapter_idx, c->current_chapter_size);
c->chapter_idx = c->chapter_idx + 1;
avio_skip(s->pb, 4); // data start offset
pos += 8;
c->current_codec_second_size = c->codec_second_size;
}
@ -267,10 +297,56 @@ static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
if (ret < 0)
return ret;
memcpy(pkt->data, buf, written);
pkt->pos = pos;
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, chapter_size;
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_size = ch->end / TIMEPREC - ch->start / TIMEPREC;
chapter_pos = av_rescale_rnd((timestamp - ch->start) / TIMEPREC,
1, c->codec_second_size,
(flags & AVSEEK_FLAG_BACKWARD) ? AV_ROUND_DOWN : AV_ROUND_UP)
* c->codec_second_size;
if (chapter_pos >= chapter_size)
chapter_pos = chapter_size;
chapter_start = c->content_start + (ch->start / TIMEPREC) + CHAPTER_HEADER_SIZE * (1 + chapter_idx);
// reinit read state
avio_seek(s->pb, chapter_start + chapter_pos, SEEK_SET);
c->current_codec_second_size = c->codec_second_size;
c->current_chapter_size = chapter_size - chapter_pos;
c->chapter_idx = 1 + chapter_idx;
ff_update_cur_dts(s, s->streams[0], ch->start + chapter_pos * TIMEPREC);
return 1;
}
static int aa_probe(AVProbeData *p)
{
uint8_t *buf = p->buf;
@ -316,6 +392,7 @@ 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,
};