| Message ID | 20220203184450.5491-13-scott.the.elm@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | rewrite avpriv_find_start_code() for clarity | expand |
Scott Theisen: > If the last four bytes form a valid start code, the loop would run another time. > Since (start == buf_end), start_code is invalidated so the loop terminates. > > However, calling avpriv_find_start_code() with p == end, it will immediately > return due to the zero size buffer. Thus the history is not needed. > --- > libavcodec/cbs_mpeg2.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c > index f2efedde5d..bf95fb7546 100644 > --- a/libavcodec/cbs_mpeg2.c > +++ b/libavcodec/cbs_mpeg2.c > @@ -168,8 +168,9 @@ static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx, > // the next unit will be treated as the last unit. > start_code = 0; > } > - > - end = avpriv_find_start_code(start, buf_end, &start_code, 0); > + else { > + end = avpriv_find_start_code(start, buf_end, &start_code, 1); > + } > start--; > // decrement so start points to the byte containing the start_code_identifier > // (may be the last byte of fragment->data); end points to the byte end is now uninitialized in case of a unit consisting solely of a Sequence End. - Andreas
On 2/4/22 21:24, Andreas Rheinhardt wrote: > end is now uninitialized in case of a unit consisting solely of a > Sequence End. I hadn't noticed that. However, I immediately restored it in the next patch.
diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c index f2efedde5d..bf95fb7546 100644 --- a/libavcodec/cbs_mpeg2.c +++ b/libavcodec/cbs_mpeg2.c @@ -168,8 +168,9 @@ static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx, // the next unit will be treated as the last unit. start_code = 0; } - - end = avpriv_find_start_code(start, buf_end, &start_code, 0); + else { + end = avpriv_find_start_code(start, buf_end, &start_code, 1); + } start--; // decrement so start points to the byte containing the start_code_identifier // (may be the last byte of fragment->data); end points to the byte