| Message ID | 20180621165826.1714-3-ottoka@posteo.de |
|---|---|
| State | Superseded |
| Headers | show |
On Thu, Jun 21, 2018 at 06:58:25PM +0200, Karsten Otto wrote: > 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. IIUC this would be linearly reading through the whole file before playing anything? if thats the case, thats not ideal, is that unavoidable ? > > 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 | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 83 insertions(+), 4 deletions(-) > > diff --git a/libavformat/aadec.c b/libavformat/aadec.c > index 4db71b1939..b009c9deca 100644 > --- a/libavformat/aadec.c > +++ b/libavformat/aadec.c > @@ -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; > @@ -172,19 +175,23 @@ 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 * TIMEPREC); > 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 * TIMEPREC); > 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 * TIMEPREC); see avpriv_set_pts_info() [...]
> Am 02.07.2018 um 10:22 schrieb Michael Niedermayer <michael@niedermayer.cc>: > > Signierter PGP-Teil > On Thu, Jun 21, 2018 at 06:58:25PM +0200, Karsten Otto wrote: >> 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. > > IIUC this would be linearly reading through the whole file before playing > anything? > if thats the case, thats not ideal, is that unavoidable ? > It is not quite as bad: A chapter header contains the byte size of the chapter, so after reading it I can avio_skip() ahead to the next chapter header, and repeat. So, this is not a linear read, but mostly a sequence of seek operations. I am aware this is not a perfect solution, but unfortunately at the current level of knowledge about the aa format, this is indeed unavoidable for now. Possibly it could be improved later if anyone gains a deeper understanding of the format. > > >> >> 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 | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++--- >> 1 file changed, 83 insertions(+), 4 deletions(-) >> >> diff --git a/libavformat/aadec.c b/libavformat/aadec.c >> index 4db71b1939..b009c9deca 100644 >> --- a/libavformat/aadec.c >> +++ b/libavformat/aadec.c >> @@ -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; > >> @@ -172,19 +175,23 @@ 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 * TIMEPREC); >> 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 * TIMEPREC); >> 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 * TIMEPREC); > > see avpriv_set_pts_info() > Thanks, I will check it out. > > [...] > -- > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB > > Elect your leaders based on what they did after the last election, not > based on what they say before an election. > > >
diff --git a/libavformat/aadec.c b/libavformat/aadec.c index 4db71b1939..b009c9deca 100644 --- a/libavformat/aadec.c +++ b/libavformat/aadec.c @@ -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; @@ -172,19 +175,23 @@ 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 * TIMEPREC); 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 * TIMEPREC); 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 * TIMEPREC); st->need_parsing = AVSTREAM_PARSE_FULL_RAW; } @@ -198,7 +205,30 @@ 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 * 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 +245,10 @@ 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 +261,7 @@ 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 +299,56 @@ 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 +394,7 @@ 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, };