[FFmpeg-devel] [PATCH] movtextdec.c: Add support for font names

[Niklesh Lalwani]

On Thu, Aug 6, 2015 at 2:02 AM, Philip Langdale <philipl at overt.org> wrote:

> On Thu, 6 Aug 2015 00:12:07 +0530
> Niklesh Lalwani <lalwani1994 at gmail.com> wrote:
>
> > From 90f466bb6a5d3cd24d7ea4d9fd8a2915cc68cdb2 Mon Sep 17 00:00:00 2001
> > From: Niklesh <niklesh.lalwani at iitb.ac.in>
> > Date: Thu, 6 Aug 2015 00:06:15 +0530
> > Subject: [PATCH] movtextdec.c: Add support for font names
> >
> > Signed-off-by: Niklesh <niklesh.lalwani at iitb.ac.in>
> > ---
> >  libavcodec/movtextdec.c | 109
> > ++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 106
> > insertions(+), 3 deletions(-)
> >
> > diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
> > index 869358c..451056c 100644
> > --- a/libavcodec/movtextdec.c
> > +++ b/libavcodec/movtextdec.c
> > @@ -36,10 +36,17 @@
> >  #define HCLR_BOX   (1<<2)
> >
> >  typedef struct {
> > +    uint16_t fontID;
> > +    uint8_t font_name_length;
> > +    uint8_t font[20];
> > +} FontRecord;
> > +
> > +typedef struct {
> >      uint16_t style_start;
> >      uint16_t style_end;
> >      uint8_t style_flag;
> >      uint8_t fontsize;
> > +    uint16_t style_fontID;
> >  } StyleBox;
> >
> >  typedef struct {
> > @@ -56,11 +63,13 @@ typedef struct {
> >      StyleBox *s_temp;
> >      HighlightBox h;
> >      HilightcolorBox c;
> > +    FontRecord **ftab;
> > +    FontRecord *ftab_temp;
> >      uint8_t box_flags;
> > -    uint16_t style_entries;
> > +    uint16_t style_entries, ftab_entries;
> >      uint64_t tracksize;
> >      int size_var;
> > -    int count_s;
> > +    int count_s, count_f;
> >  } MovTextContext;
> >
> >  typedef struct {
> > @@ -80,6 +89,80 @@ static void mov_text_cleanup(MovTextContext *m)
> >      }
> >  }
> >
> > +static void mov_text_cleanup_ftab(MovTextContext *m)
> > +{
> > +    int i;
> > +    for(i = 0; i < m->count_f; i++) {
> > +        av_freep(&m->ftab[i]);
> > +    }
> > +    av_freep(&m->ftab);
> > +}
> > +
> > +static int mov_text_t3xg(AVCodecContext *avctx, MovTextContext *m)
>
> I'm pretty sure it's "tx3g"
>
> > +{
> > +    char *t3xg_ptr = avctx->extradata;
> > +    int i, tracksize;
> > +
> > +    tracksize = 38; /* Size till ftab_entries */
>
> I'd say box size. It's not technically a track.
>
> And make the 38 a constant.
>
> > +    if (avctx->extradata_size < tracksize)
> > +        return -1;
> > +
> > +    m->ftab_entries = 0;
> > +    // Display Flags
> > +    t3xg_ptr += 4;
> > +    // Alignment
> > +    t3xg_ptr += 2;
> > +    // Background Color
> > +    t3xg_ptr += 4;
> > +    // BoxRecord
> > +    t3xg_ptr += 8;
> > +    // StyleRecord
> > +    t3xg_ptr += 12;
> > +    // FontRecord
> > +    // FontRecord Size
> > +    t3xg_ptr += 4;
> > +    // ftab
> > +    t3xg_ptr += 4;
> > +
> > +    tracksize += 2;
> > +    if (avctx->extradata_size < tracksize)
> > +        return -1;
>
> Why not just initialize tracksize to 40? The extra += 2 isn't optional.
>
> > +
> > +    m->ftab_entries = AV_RB16(t3xg_ptr);
> > +    t3xg_ptr += 2;
> > +
> > +    for (i = 0; i < m->ftab_entries; i++) {
> > +
> > +        tracksize += 3;
> > +        if (avctx->extradata_size < tracksize) {
> > +            m->ftab_entries = 0;
> > +            return -1;
> > +        }
>
> You need to clean up any ftab entries that have already been processed.
>
> > +        m->ftab_temp = av_malloc(sizeof(*m->ftab_temp));
> > +        if (!m->ftab_temp) {
> > +            mov_text_cleanup_ftab(m);
> > +            return AVERROR(ENOMEM);
> > +        }
> > +        m->ftab_temp->fontID = AV_RB16(t3xg_ptr);
> > +        t3xg_ptr += 2;
> > +        m->ftab_temp->font_name_length = *t3xg_ptr++;
> > +
> > +        tracksize = tracksize + m->ftab_temp->font_name_length;
> > +        if ((avctx->extradata_size < tracksize) ||
> > (m->ftab_temp->font_name_length > 20)) {
> > +            m->ftab_entries = 0;
> > +            return -1;
> > +        }
> > +        memcpy(m->ftab_temp->font, t3xg_ptr,
> > m->ftab_temp->font_name_length);
> > +        av_dynarray_add(&m->ftab, &m->count_f, m->ftab_temp);
> > +        if (!m->ftab) {
> > +            mov_text_cleanup_ftab(m);
> > +            return AVERROR(ENOMEM);
> > +        }
>
> I didn't think about this before, but there's no need to store the font
> name and length in your FontRecord in this way. Just store it as a
> normal null terminated string. Then you don't need the size and do can
> do normal string manipulation on it later (like using av_bprintf with
> '%s').
>

Yes, I can do that and add a null character at the end after memcopy, but I
thought I'll define the structs as close as possible to the Records defined
in 3GPP spec.
Also, I think I should not limit the length to 20. Ideally, it is a uint8_t
value. In that case, I'll need to malloc the size of font length.

Rest all updated.

Thanks,
Niklesh


> > +        t3xg_ptr = t3xg_ptr + 3 + m->ftab[i]->font_name_length;
> > +    }
>
>