[vdr] Re: Nasty bug in StillPicture()

[Oliver Endriss <o.endriss@gmx.de>]

On Sunday 19 October 2003 13:22, Thomas Heiligenmann wrote:
> ...

The new code looks like this:

              if ((Data[i + 3] & 0xF0) == 0xE0) { // video packet
                 // skip PES header
                 int offs = i + 6;
                 // skip header extension
                 if ((Data[i + 6] & 0xC0) == 0x80) {
                    // MPEG-2 PES header
                    if (Data[i + 8] >= Length)
                       break;
                    offs += 3;
                    offs += Data[i + 8];
                    len -= 3;
                    len -= Data[i + 8];
                    if (len < 0 || offs + len >= Length)
                       break;
                    }
                 else {
                    // MPEG-1 PES header
                    while (offs < Length && len > 0 && Data[offs] == 0xFF) {
                          offs++;
                          len--;
                          }
                    if (offs <= Length - 2 && len >= 2 && (Data[offs] & 0xC0) == 0x40) {
                       offs += 2;
                       len -= 2;
                       }
                    if (offs <= Length - 5 && len >= 5 && (Data[offs] & 0xF0) == 0x20) {
                       offs += 5;
                       len -= 5;
                       }
                    else if (offs <= Length - 10 && len >= 10 && (Data[offs] & 0xF0) == 0x30) {
                       offs += 10;
                       len -= 10;
                       }
                    else if (offs < Length && len > 0) {
[*]-->                 offs++;
                       len--;
                       }
                    }
                 if (blen + len > Length) // invalid PES length field
                    break;
                 memcpy(&buf[blen], &Data[offs], len);
                 i = offs + len;
                 blen += len;
                 }

I don't have MPEG-1 data, but one question: ;-)
Is it correct to unconditionally remove one byte [*] if none of the
previous if-else constructs apply? For example, we always skip one
byte if there is no MPEG-2 header.

Oliver


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