Make sure this does not break existing files,
On 8/11/20, Andreas Rheinhardt <andreas.rheinha...@gmail.com> wrote:
> Up until now, the TiVo demuxer parse an array of SEQ entries, yet it has
> never ever made any use of them. In fact, parse_master, the function
> parsing said table, only influenced the outside world in three ways: Via
> an excessive amount of error message in case a certain parameter is not
> what it expected; via an allocation (the aforementioned write-only
> array); and by setting a certain parameter (ty->cur_chunk_pos), but that
> parameter is always overwritten before it is used (it is overwritten
> in get_chunk() on success and if get_chunk() fails, the error is
> returned to the caller anyway). So remove the array and the function
> used to parse it.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
> ---
> Furthermore, the parsing code seems not to work at all: The current
> position is not incremented by map_size if map_size <= 8.
>
> libavformat/ty.c | 68 +-----------------------------------------------
> 1 file changed, 1 insertion(+), 67 deletions(-)
>
> diff --git a/libavformat/ty.c b/libavformat/ty.c
> index 738a22e7de..c8e1067c0e 100644
> --- a/libavformat/ty.c
> +++ b/libavformat/ty.c
> @@ -72,11 +72,6 @@ typedef enum {
> TIVO_AUDIO_MPEG
> } TiVo_audio;
>
> -typedef struct TySeqTable {
> - uint64_t timestamp;
> - uint8_t chunk_bitmask[8];
> -} TySeqTable;
> -
> typedef struct TYDemuxContext {
> unsigned cur_chunk;
> unsigned cur_chunk_pos;
> @@ -90,7 +85,6 @@ typedef struct TYDemuxContext {
> int pes_buf_cnt; /* how many bytes in our buffer */
> size_t ac3_pkt_size; /* length of ac3 pkt we've seen so
> far */
> uint64_t last_ty_pts; /* last TY timestamp we've seen */
> - unsigned seq_table_size; /* number of entries in SEQ table */
>
> int64_t first_audio_pts;
> int64_t last_audio_pts;
> @@ -99,8 +93,6 @@ typedef struct TYDemuxContext {
> TyRecHdr *rec_hdrs; /* record headers array */
> int cur_rec; /* current record in this chunk */
> int num_recs; /* number of recs in this chunk */
> - int seq_rec; /* record number where seq start is
> */
> - TySeqTable *seq_table; /* table of SEQ entries from mstr chk
> */
> int first_chunk;
>
> uint8_t chunk[CHUNK_SIZE];
> @@ -339,58 +331,6 @@ static int ty_read_header(AVFormatContext *s)
> return 0;
> }
>
> -/* parse a master chunk, filling the SEQ table and other variables.
> - * We assume the stream is currently pointing to it.
> - */
> -static void parse_master(AVFormatContext *s)
> -{
> - TYDemuxContext *ty = s->priv_data;
> - unsigned map_size; /* size of bitmask, in bytes */
> - unsigned i, j;
> -
> - /* Note that the entries in the SEQ table in the stream may have
> - different sizes depending on the bits per entry. We store them
> - all in the same size structure, so we have to parse them out one
> - by one. If we had a dynamic structure, we could simply read the
> - entire table directly from the stream into memory in place. */
> -
> - /* clear the SEQ table */
> - av_freep(&ty->seq_table);
> -
> - /* parse header info */
> -
> - map_size = AV_RB32(ty->chunk + 20); /* size of bitmask, in bytes */
> - i = AV_RB32(ty->chunk + 28); /* size of SEQ table, in bytes */
> -
> - ty->seq_table_size = i / (8LL + map_size);
> -
> - if (ty->seq_table_size == 0) {
> - ty->seq_table = NULL;
> - return;
> - }
> -
> - /* parse all the entries */
> - ty->seq_table = av_calloc(ty->seq_table_size, sizeof(TySeqTable));
> - if (ty->seq_table == NULL) {
> - ty->seq_table_size = 0;
> - return;
> - }
> -
> - ty->cur_chunk_pos = 32;
> - for (j = 0; j < ty->seq_table_size; j++) {
> - if (ty->cur_chunk_pos >= CHUNK_SIZE - 8)
> - return;
> - ty->seq_table[j].timestamp = AV_RB64(ty->chunk +
> ty->cur_chunk_pos);
> - ty->cur_chunk_pos += 8;
> - if (map_size > 8) {
> - av_log(s, AV_LOG_ERROR, "Unsupported SEQ bitmap size in master
> chunk.\n");
> - ty->cur_chunk_pos += map_size;
> - } else {
> - memcpy(ty->seq_table[j].chunk_bitmask, ty->chunk +
> ty->cur_chunk_pos, map_size);
> - }
> - }
> -}
> -
> static int get_chunk(AVFormatContext *s)
> {
> TYDemuxContext *ty = s->priv_data;
> @@ -413,7 +353,7 @@ static int get_chunk(AVFormatContext *s)
>
> /* check if it's a PART Header */
> if (AV_RB32(ty->chunk) == TIVO_PES_FILEID) {
> - parse_master(s); /* parse master chunk */
> + /* skip master chunk and read new chunk */
> return get_chunk(s);
> }
>
> @@ -421,14 +361,9 @@ static int get_chunk(AVFormatContext *s)
> if (ty->chunk[3] & 0x80) {
> /* 16 bit rec cnt */
> ty->num_recs = num_recs = (ty->chunk[1] << 8) + ty->chunk[0];
> - ty->seq_rec = (ty->chunk[3] << 8) + ty->chunk[2];
> - if (ty->seq_rec != 0xffff) {
> - ty->seq_rec &= ~0x8000;
> - }
> } else {
> /* 8 bit reclen - TiVo 1.3 format */
> ty->num_recs = num_recs = ty->chunk[0];
> - ty->seq_rec = ty->chunk[1];
> }
> ty->cur_rec = 0;
> ty->first_chunk = 0;
> @@ -770,7 +705,6 @@ static int ty_read_close(AVFormatContext *s)
> {
> TYDemuxContext *ty = s->priv_data;
>
> - av_freep(&ty->seq_table);
> av_freep(&ty->rec_hdrs);
>
> return 0;
> --
> 2.20.1
>
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