[FFmpeg-devel] [PATCH v3 2/3] aadec: add chapters and seeking

[Michael Niedermayer]

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()


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Elect your leaders based on what they did after the last election, not
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