Pekka Väänänen:
> High color 15-bit VQA3 video streams contain high level chunks with
> only codebook updates that shouldn't be considered new frames. Now
> the demuxer stores a reference to such VQFL chunks and returns them
> later along with a VQFR chunk with full frame data.
> ---
> libavformat/westwood_vqa.c | 51 ++++++++++++++++++++++++++++++++++++--
> 1 file changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/westwood_vqa.c b/libavformat/westwood_vqa.c
> index 77df007c11..cc859c58ca 100644
> --- a/libavformat/westwood_vqa.c
> +++ b/libavformat/westwood_vqa.c
> @@ -1,6 +1,7 @@
> /*
> * Westwood Studios VQA Format Demuxer
> - * Copyright (c) 2003 The FFmpeg project
> + * Copyright (c) 2003 Mike Melanson <melan...@pcisys.net>
> + * Copyright (c) 2021 Pekka Väänänen <pekka.vaana...@iki.fi>
> *
> * This file is part of FFmpeg.
> *
> @@ -30,6 +31,7 @@
>
> #include "libavutil/intreadwrite.h"
> #include "avformat.h"
> +#include "avio_internal.h"
> #include "internal.h"
>
> #define FORM_TAG MKBETAG('F', 'O', 'R', 'M')
> @@ -40,6 +42,7 @@
> #define SND1_TAG MKBETAG('S', 'N', 'D', '1')
> #define SND2_TAG MKBETAG('S', 'N', 'D', '2')
> #define VQFR_TAG MKBETAG('V', 'Q', 'F', 'R')
> +#define VQFL_TAG MKBETAG('V', 'Q', 'F', 'L')
>
> /* don't know what these tags are for, but acknowledge their existence */
> #define CINF_TAG MKBETAG('C', 'I', 'N', 'F')
> @@ -60,6 +63,8 @@ typedef struct WsVqaDemuxContext {
> int sample_rate;
> int audio_stream_index;
> int video_stream_index;
> + int64_t vqfl_chunk_pos;
> + int vqfl_chunk_size;
> } WsVqaDemuxContext;
>
> static int wsvqa_probe(const AVProbeData *p)
> @@ -120,6 +125,8 @@ static int wsvqa_read_header(AVFormatContext *s)
> wsvqa->channels = header[26];
> wsvqa->bps = header[27];
> wsvqa->audio_stream_index = -1;
> + wsvqa->vqfl_chunk_pos = 0;
> + wsvqa->vqfl_chunk_size = 0;
>
> s->ctx_flags |= AVFMTCTX_NOHEADER;
>
> @@ -172,7 +179,21 @@ static int wsvqa_read_packet(AVFormatContext *s,
>
> skip_byte = chunk_size & 0x01;
>
> - if ((chunk_type == SND0_TAG) || (chunk_type == SND1_TAG) ||
> + if (chunk_type == VQFL_TAG) {
> + /* Each VQFL chunk carries only a codebook update inside which
> must be applied
> + * before the next VQFR is rendered. That's why we stash the
> VQFL offset here
> + * so it can be combined with the next VQFR packet. This way
> each packet
> + * includes a whole frame as expected. */
> + wsvqa->vqfl_chunk_pos = avio_tell(pb);
> + wsvqa->vqfl_chunk_size = (int)(chunk_size);
> + if (wsvqa->vqfl_chunk_size < 0 || wsvqa->vqfl_chunk_size > 3 *
> (1 << 20))
> + return AVERROR_INVALIDDATA;
> + /* We need a big seekback buffer because there can be SNxx, VIEW
> and ZBUF
> + * chunks in the stream before we reach VQFR and seek back here.
> */
This code also reads the VQFR chunk before seeking back, so this needs
to be changed or accounted for.
> + ffio_ensure_seekback(pb, wsvqa->vqfl_chunk_size + 512 * 1024);
> + avio_skip(pb, chunk_size + skip_byte);
> + continue;
> + } else if ((chunk_type == SND0_TAG) || (chunk_type == SND1_TAG) ||
> (chunk_type == SND2_TAG) || (chunk_type == VQFR_TAG)) {
>
> ret= av_get_packet(pb, pkt, chunk_size);
> @@ -235,6 +256,32 @@ static int wsvqa_read_packet(AVFormatContext *s,
> }
> break;
> case VQFR_TAG:
> + /* if a new codebook is available inside an earlier a VQFL
> chunk then
> + * prepend it to 'pkt' */
> + if (wsvqa->vqfl_chunk_size > 0) {
> + int64_t current_pos = pkt->pos;
> + int current_size = pkt->size;
> +
> + if (avio_seek(pb, wsvqa->vqfl_chunk_pos, SEEK_SET) < 0)
> + return AVERROR(EIO);
> +
> + /* the decoder expects chunks to be 16-bit aligned */
> + if (wsvqa->vqfl_chunk_size % 2 == 1)
> + wsvqa->vqfl_chunk_size++;
> +
> + av_packet_unref(pkt);
This fixes the memleak, yet the main data is still read twice.
> + if (av_get_packet(pb, pkt, wsvqa->vqfl_chunk_size) < 0)
> + return AVERROR(EIO);
> +
> + if (avio_seek(pb, current_pos, SEEK_SET) < 0)
> + return AVERROR(EIO);
> +
> + ret = av_append_packet(pb, pkt, current_size);
> +
> + wsvqa->vqfl_chunk_pos = 0;
> + wsvqa->vqfl_chunk_size = 0;
> + }
> +
> pkt->stream_index = wsvqa->video_stream_index;
> pkt->duration = 1;
> break;
>
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