On Wed, Aug 28, 2019 at 11:12:51PM +0800, Kah Goh wrote:
> There are differing standards that define different starting line
> numbers. For example, VSF TR-03 says the line numbers starts at 1,
> whereas SMPTE 2110-20 says it should start at 0.
>
> This change fixes the following issues when the line numbering start
> at 1:
> - The first scan line was being incorrectly interpreted as the second
> scan line. This means the first line in the frame was never being
> populated.
> - The last packet for the video frame would be treated as invalid
> because it would have been copied outside of the frame. Consequently,
> the packet would never be "finalized" and the next packet triggers a
> missed RTP marker ("Missed previous RTP marker" would keep being
> logged).
>
> VSF TR-03:
> http://www.videoservicesforum.org/download/technical_recommendations/VSF_TR-03_2015-11-12.pdf
>
> Co-Authored-By: Jacob Siddall <k...@live.com.au>
> Co-Authored-By: Kah Goh <villas...@yahoo.com.au>
> Signed-off-by: Kah Goh <villas...@yahoo.com.au>
> ---
> libavformat/rtpdec_rfc4175.c | 41 +++++++++++++++++++++++++++++++++---
> 1 file changed, 38 insertions(+), 3 deletions(-)
>
> diff --git a/libavformat/rtpdec_rfc4175.c b/libavformat/rtpdec_rfc4175.c
> index e9c62c1389..427d4b31e2 100644
> --- a/libavformat/rtpdec_rfc4175.c
> +++ b/libavformat/rtpdec_rfc4175.c
> @@ -25,6 +25,7 @@
> #include "rtpdec_formats.h"
> #include "libavutil/avstring.h"
> #include "libavutil/pixdesc.h"
> +#include <stdbool.h>
>
> struct PayloadContext {
> char *sampling;
> @@ -37,6 +38,12 @@ struct PayloadContext {
> unsigned int pgroup; /* size of the pixel group in bytes */
> unsigned int xinc;
>
> + /* The line number of the first line in the frame (usually either 0 or
> 1). */
> + int first_line_number;
> +
> + /* This is set to true once the first line number is confirmed. */
> + bool first_line_number_known;
> +
> uint32_t timestamp;
> };
>
> @@ -136,6 +143,13 @@ static int rfc4175_finalize_packet(PayloadContext *data,
> AVPacket *pkt,
> return ret;
> }
>
> +static int rfc4175_initialize(AVFormatContext *s, int st_index,
> PayloadContext *data)
> +{
> + data->first_line_number = 0;
> + data->first_line_number_known = false;
> + return 0;
> +}
> +
> static int rfc4175_handle_packet(AVFormatContext *ctx, PayloadContext *data,
> AVStream *st, AVPacket *pkt, uint32_t
> *timestamp,
> const uint8_t * buf, int len,
> @@ -199,6 +213,11 @@ static int rfc4175_handle_packet(AVFormatContext *ctx,
> PayloadContext *data,
> cont = headers[4] & 0x80;
> headers += 6;
>
> + if (line == 0) {
> + data->first_line_number = 0;
> + data->first_line_number_known = true;
> + }
> +
> if (length % data->pgroup)
> return AVERROR_INVALIDDATA;
>
> @@ -206,9 +225,15 @@ static int rfc4175_handle_packet(AVFormatContext *ctx,
> PayloadContext *data,
> length = payload_len;
>
> /* prevent ill-formed packets to write after buffer's end */
> - copy_offset = (line * data->width + offset) * data->pgroup /
> data->xinc;
> - if (copy_offset + length > data->frame_size)
> - return AVERROR_INVALIDDATA;
> + copy_offset = ((line - data->first_line_number) * data->width +
> offset) * data->pgroup / data->xinc;
> + if (copy_offset + length > data->frame_size) {
> + if (data->first_line_number_known)
> + return AVERROR_INVALIDDATA;
> +
> + // This would happen if the line numbering is 1 based. We still
> need to check for the RTP flag
> + // marker (as per after the while loop).
> + break;
> + }
>
> dest = data->frame + copy_offset;
> memcpy(dest, payload, length);
> @@ -218,6 +243,15 @@ static int rfc4175_handle_packet(AVFormatContext *ctx,
> PayloadContext *data,
> } while (cont);
>
> if ((flags & RTP_FLAG_MARKER)) {
> + if (!data->first_line_number_known) {
> + data->first_line_number = line - data->height + 1;
> + if (data->first_line_number < 0) {
> + // This could happen if the frame does not fill up the
> entire height.
> + data->first_line_number = 0;
> + av_log(ctx, AV_LOG_WARNING, "Video frame does not fill
> entire height");
> + }
> + data->first_line_number_known = true;
What if the last line is larger than height ?
first_line_number is only checked for <0 not >1 nor >height
but maybe ive missed some check
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
The bravest are surely those who have the clearest vision
of what is before them, glory and danger alike, and yet
notwithstanding go out to meet it. -- Thucydides
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