On 2016-03-21 15:00:21 +0100, Anton Khirnov wrote:
> This is required by h264.
> ---
> libavcodec/h2645_parse.c | 38 +++++++++++++++++++++++++++++++++++---
> libavcodec/h2645_parse.h | 6 ++++++
> 2 files changed, 41 insertions(+), 3 deletions(-)
>
> diff --git a/libavcodec/h2645_parse.c b/libavcodec/h2645_parse.c
> index 6be79ac..88eb78a 100644
> --- a/libavcodec/h2645_parse.c
> +++ b/libavcodec/h2645_parse.c
> @@ -22,13 +22,12 @@
>
> #include "config.h"
>
> +#include "libavutil/intmath.h"
> #include "libavutil/intreadwrite.h"
> #include "libavutil/mem.h"
>
> #include "h2645_parse.h"
>
> -/* FIXME: This is adapted from ff_h264_decode_nal, avoiding duplication
> - * between these functions would be nice. */
> int ff_h2645_extract_rbsp(const uint8_t *src, int length,
> H2645NAL *nal)
> {
> @@ -128,6 +127,30 @@ nsc:
> return si;
> }
>
> +static int get_bit_length(H2645NAL *nal, int skip_padding_zeros)
> +{
> + int size = nal->size;
> + int v;
> +
> + while (skip_padding_zeros && size > 0 && nal->data[size - 1] == 0)
> + size--;
> +
> + if (!size)
> + return 0;
> +
> + v = nal->data[size - 1];
> +
> + if (size > INT_MAX / 8)
> + return AVERROR(ERANGE);
> + size *= 8;
> +
> + /* remove the stop bit and following trailing zeros */
maybe add "or nothing for damaged bitstreams". the 'if (v)' is a little
too tricky for my taste. It also limits the av_ctz() to 8.
> + if (v)
> + size -= av_ctz(v) + 1;
> +
> + return size;
> +}
> +
> /**
> * @return AVERROR_INVALIDDATA if the packet is not a valid NAL unit,
> * 0 if the unit should be skipped, 1 otherwise
> @@ -181,6 +204,7 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t
> *buf, int length,
> while (length >= 4) {
> H2645NAL *nal;
> int extract_length = 0;
> + int skip_trailing_zeros = 1;
is there a reason to use two different names for the same thing?
>
> if (is_nalff) {
> int i;
> @@ -224,7 +248,15 @@ int ff_h2645_packet_split(H2645Packet *pkt, const
> uint8_t *buf, int length,
> if (consumed < 0)
> return consumed;
>
> - ret = init_get_bits8(&nal->gb, nal->data, nal->size);
> + /* see commit 3566042a0 */
> + if (consumed < length - 3 &&
> + buf[consumed] == 0x00 && buf[consumed + 1] == 0x00 &&
> + buf[consumed + 2] == 0x01 && buf[consumed + 3] == 0xE0)
> + skip_trailing_zeros = 0;
> +
> + nal->size_bits = get_bit_length(nal, skip_trailing_zeros);
> +
> + ret = init_get_bits(&nal->gb, nal->data, nal->size_bits);
> if (ret < 0)
> return ret;
>
> diff --git a/libavcodec/h2645_parse.h b/libavcodec/h2645_parse.h
> index 148ccf3..651cf26 100644
> --- a/libavcodec/h2645_parse.h
> +++ b/libavcodec/h2645_parse.h
> @@ -33,6 +33,12 @@ typedef struct H2645NAL {
> int size;
> const uint8_t *data;
>
> + /**
> + * Size, in bits, of just the data, excluding the stop bit and any
> trailing
> + * padding. I.e. what HEVC calls SODB.
> + */
> + int size_bits;
> +
> int raw_size;
> const uint8_t *raw_data;
>
Janne
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