| Message ID | 20191117073440.22718-6-andreas.rheinhardt@gmail.com |
|---|---|
| State | Accepted |
| Headers | show |
On 17/11/2019 07:34, Andreas Rheinhardt wrote: > This is possible because the size of a scan header is always a multiple > of a byte. > > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> > --- > libavcodec/cbs_jpeg.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/libavcodec/cbs_jpeg.c b/libavcodec/cbs_jpeg.c > index b189cbd9b7..64fe70beab 100644 > --- a/libavcodec/cbs_jpeg.c > +++ b/libavcodec/cbs_jpeg.c > @@ -330,7 +330,7 @@ static int cbs_jpeg_write_scan(CodedBitstreamContext *ctx, > PutBitContext *pbc) > { > JPEGRawScan *scan = unit->content; > - int i, err; > + int err; > > err = cbs_jpeg_write_scan_header(ctx, pbc, &scan->header); > if (err < 0) > @@ -340,8 +340,12 @@ static int cbs_jpeg_write_scan(CodedBitstreamContext *ctx, > if (scan->data_size * 8 > put_bits_left(pbc)) > return AVERROR(ENOSPC); > > - for (i = 0; i < scan->data_size; i++) > - put_bits(pbc, 8, scan->data[i]); > + av_assert0(put_bits_count(pbc) % 8 == 0); > + > + flush_put_bits(pbc); Doesn't this pad to a word boundary? (It looks like that's coincidentally fine for a 3-component JPEG, but not in general.) > + > + memcpy(put_bits_ptr(pbc), scan->data, scan->data_size); > + skip_put_bytes(pbc, scan->data_size); > } > > return 0; > - Mark
On Mon, Nov 18, 2019 at 1:02 AM Mark Thompson <sw@jkqxz.net> wrote: > On 17/11/2019 07:34, Andreas Rheinhardt wrote: > > This is possible because the size of a scan header is always a multiple > > of a byte. > > > > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> > > --- > > libavcodec/cbs_jpeg.c | 10 +++++++--- > > 1 file changed, 7 insertions(+), 3 deletions(-) > > > > diff --git a/libavcodec/cbs_jpeg.c b/libavcodec/cbs_jpeg.c > > index b189cbd9b7..64fe70beab 100644 > > --- a/libavcodec/cbs_jpeg.c > > +++ b/libavcodec/cbs_jpeg.c > > @@ -330,7 +330,7 @@ static int cbs_jpeg_write_scan(CodedBitstreamContext > *ctx, > > PutBitContext *pbc) > > { > > JPEGRawScan *scan = unit->content; > > - int i, err; > > + int err; > > > > err = cbs_jpeg_write_scan_header(ctx, pbc, &scan->header); > > if (err < 0) > > @@ -340,8 +340,12 @@ static int > cbs_jpeg_write_scan(CodedBitstreamContext *ctx, > > if (scan->data_size * 8 > put_bits_left(pbc)) > > return AVERROR(ENOSPC); > > > > - for (i = 0; i < scan->data_size; i++) > > - put_bits(pbc, 8, scan->data[i]); > > + av_assert0(put_bits_count(pbc) % 8 == 0); > > + > > + flush_put_bits(pbc); > > Doesn't this pad to a word boundary? (It looks like that's coincidentally > fine for a 3-component JPEG, but not in general.) > > No, it doesn't. It just writes everything in its cache, filling any unset bits in the last byte with zero. And it does so by writing single bytes at a time. - Andreas
diff --git a/libavcodec/cbs_jpeg.c b/libavcodec/cbs_jpeg.c index b189cbd9b7..64fe70beab 100644 --- a/libavcodec/cbs_jpeg.c +++ b/libavcodec/cbs_jpeg.c @@ -330,7 +330,7 @@ static int cbs_jpeg_write_scan(CodedBitstreamContext *ctx, PutBitContext *pbc) { JPEGRawScan *scan = unit->content; - int i, err; + int err; err = cbs_jpeg_write_scan_header(ctx, pbc, &scan->header); if (err < 0) @@ -340,8 +340,12 @@ static int cbs_jpeg_write_scan(CodedBitstreamContext *ctx, if (scan->data_size * 8 > put_bits_left(pbc)) return AVERROR(ENOSPC); - for (i = 0; i < scan->data_size; i++) - put_bits(pbc, 8, scan->data[i]); + av_assert0(put_bits_count(pbc) % 8 == 0); + + flush_put_bits(pbc); + + memcpy(put_bits_ptr(pbc), scan->data, scan->data_size); + skip_put_bytes(pbc, scan->data_size); } return 0;
This is possible because the size of a scan header is always a multiple of a byte. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> --- libavcodec/cbs_jpeg.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)