* [FFmpeg-devel] [PATCH] avcodec/photocd: allow decoding vlc with errors
@ 2023-09-27 19:53 Paul B Mahol
2023-09-28 9:37 ` Anton Khirnov
0 siblings, 1 reply; 4+ messages in thread
From: Paul B Mahol @ 2023-09-27 19:53 UTC (permalink / raw)
To: FFmpeg development discussions and patches
[-- Attachment #1: Type: text/plain, Size: 10 bytes --]
Attached.
[-- Attachment #2: 0001-avcodec-photocd-allow-decoding-vlc-with-errors.patch --]
[-- Type: text/x-patch, Size: 2296 bytes --]
From 6b7e51e2b4facead9c45fb94647c85b58e6fdf22 Mon Sep 17 00:00:00 2001
From: Paul B Mahol <onemda@gmail.com>
Date: Wed, 27 Sep 2023 21:48:49 +0200
Subject: [PATCH] avcodec/photocd: allow decoding vlc with errors
Also rename option that no longer works.
Also make tables finding more robust.
Signed-off-by: Paul B Mahol <onemda@gmail.com>
---
libavcodec/photocd.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/libavcodec/photocd.c b/libavcodec/photocd.c
index 07e8d460bd..a9e42bb86a 100644
--- a/libavcodec/photocd.c
+++ b/libavcodec/photocd.c
@@ -277,8 +277,6 @@ static av_noinline int decode_huff(AVCodecContext *avctx, AVFrame *frame,
if (get_bits_left(&g) <= 0)
return AVERROR_INVALIDDATA;
m = get_vlc2(&g, s->vlc[idx].table, s->vlc[idx].bits, 2);
- if (m < 0)
- return AVERROR_INVALIDDATA;
m = sign_extend(m, 8);
data[x] = av_clip_uint8(data[x] + m);
}
@@ -389,6 +387,7 @@ static int photocd_decode_frame(AVCodecContext *avctx, AVFrame *p,
return AVERROR_INVALIDDATA;
if (s->resolution == 4) {
+ s->streampos = (AV_RB16(avpkt->data + 2048 + 1536 + 3) + 12) * 2048;
interp_pixels(ptr, p->linesize[0], img_info[4].width, img_info[4].height);
interp_lines (ptr, p->linesize[0], img_info[4].width, img_info[4].height);
@@ -396,7 +395,7 @@ static int photocd_decode_frame(AVCodecContext *avctx, AVFrame *p,
if ((ret = read_hufftable(avctx, &s->vlc[n])) < 0)
return ret;
}
- s->streampos = (s->streampos + 2047) & ~0x3ff;
+ s->streampos = (AV_RB16(avpkt->data + 2048 + 1536 + 3) + 14) * 2048;
if (decode_huff(avctx, p, 4, 4) < 0)
return AVERROR_INVALIDDATA;
}
@@ -447,7 +446,7 @@ static av_cold int photocd_decode_close(AVCodecContext *avctx)
#define VD AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_DECODING_PARAM
static const AVOption options[] = {
- { "lowres", "Lower the decoding resolution by a power of two",
+ { "reduction", "Lower the decoding resolution by a power of two",
OFFSET(lowres), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 4, VD },
{ NULL },
};
--
2.42.0
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [FFmpeg-devel] [PATCH] avcodec/photocd: allow decoding vlc with errors
2023-09-27 19:53 [FFmpeg-devel] [PATCH] avcodec/photocd: allow decoding vlc with errors Paul B Mahol
@ 2023-09-28 9:37 ` Anton Khirnov
2023-09-28 9:48 ` Paul B Mahol
0 siblings, 1 reply; 4+ messages in thread
From: Anton Khirnov @ 2023-09-28 9:37 UTC (permalink / raw)
To: FFmpeg development discussions and patches
Quoting Paul B Mahol (2023-09-27 21:53:54)
> Attached.
>
> From 6b7e51e2b4facead9c45fb94647c85b58e6fdf22 Mon Sep 17 00:00:00 2001
> From: Paul B Mahol <onemda@gmail.com>
> Date: Wed, 27 Sep 2023 21:48:49 +0200
> Subject: [PATCH] avcodec/photocd: allow decoding vlc with errors
>
> Also rename option that no longer works.
> Also make tables finding more robust.
Why do all these things in a single patch?
And why are there no tests for this decoder?
> Signed-off-by: Paul B Mahol <onemda@gmail.com>
> ---
> libavcodec/photocd.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/libavcodec/photocd.c b/libavcodec/photocd.c
> index 07e8d460bd..a9e42bb86a 100644
> --- a/libavcodec/photocd.c
> +++ b/libavcodec/photocd.c
> @@ -277,8 +277,6 @@ static av_noinline int decode_huff(AVCodecContext *avctx, AVFrame *frame,
> if (get_bits_left(&g) <= 0)
> return AVERROR_INVALIDDATA;
> m = get_vlc2(&g, s->vlc[idx].table, s->vlc[idx].bits, 2);
> - if (m < 0)
> - return AVERROR_INVALIDDATA;
Shouldn't this error be at least logged? Perhaps it should still fail on
AV_EF_EXPLODE.
> m = sign_extend(m, 8);
> data[x] = av_clip_uint8(data[x] + m);
> }
> @@ -389,6 +387,7 @@ static int photocd_decode_frame(AVCodecContext *avctx, AVFrame *p,
> return AVERROR_INVALIDDATA;
>
> if (s->resolution == 4) {
> + s->streampos = (AV_RB16(avpkt->data + 2048 + 1536 + 3) + 12) * 2048;
Where do these magic numbers come from? Same below.
--
Anton Khirnov
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [FFmpeg-devel] [PATCH] avcodec/photocd: allow decoding vlc with errors
2023-09-28 9:37 ` Anton Khirnov
@ 2023-09-28 9:48 ` Paul B Mahol
2023-09-28 10:00 ` Anton Khirnov
0 siblings, 1 reply; 4+ messages in thread
From: Paul B Mahol @ 2023-09-28 9:48 UTC (permalink / raw)
To: FFmpeg development discussions and patches
On 9/28/23, Anton Khirnov <anton@khirnov.net> wrote:
> Quoting Paul B Mahol (2023-09-27 21:53:54)
>> Attached.
>>
>> From 6b7e51e2b4facead9c45fb94647c85b58e6fdf22 Mon Sep 17 00:00:00 2001
>> From: Paul B Mahol <onemda@gmail.com>
>> Date: Wed, 27 Sep 2023 21:48:49 +0200
>> Subject: [PATCH] avcodec/photocd: allow decoding vlc with errors
>>
>> Also rename option that no longer works.
>> Also make tables finding more robust.
>
> Why do all these things in a single patch?
>
I can boost my commits if you prefer that way.
> And why are there no tests for this decoder?
Its complicated.
>
>> Signed-off-by: Paul B Mahol <onemda@gmail.com>
>> ---
>> libavcodec/photocd.c | 7 +++----
>> 1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/libavcodec/photocd.c b/libavcodec/photocd.c
>> index 07e8d460bd..a9e42bb86a 100644
>> --- a/libavcodec/photocd.c
>> +++ b/libavcodec/photocd.c
>> @@ -277,8 +277,6 @@ static av_noinline int decode_huff(AVCodecContext
>> *avctx, AVFrame *frame,
>> if (get_bits_left(&g) <= 0)
>> return AVERROR_INVALIDDATA;
>> m = get_vlc2(&g, s->vlc[idx].table, s->vlc[idx].bits, 2);
>> - if (m < 0)
>> - return AVERROR_INVALIDDATA;
>
> Shouldn't this error be at least logged? Perhaps it should still fail on
> AV_EF_EXPLODE.
>
>> m = sign_extend(m, 8);
>> data[x] = av_clip_uint8(data[x] + m);
>> }
>> @@ -389,6 +387,7 @@ static int photocd_decode_frame(AVCodecContext *avctx,
>> AVFrame *p,
>> return AVERROR_INVALIDDATA;
>>
>> if (s->resolution == 4) {
>> + s->streampos = (AV_RB16(avpkt->data + 2048 + 1536 + 3) + 12)
>> * 2048;
>
> Where do these magic numbers come from? Same below.
From offset from internal image file bitstream table structure.
>
> --
> Anton Khirnov
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [FFmpeg-devel] [PATCH] avcodec/photocd: allow decoding vlc with errors
2023-09-28 9:48 ` Paul B Mahol
@ 2023-09-28 10:00 ` Anton Khirnov
0 siblings, 0 replies; 4+ messages in thread
From: Anton Khirnov @ 2023-09-28 10:00 UTC (permalink / raw)
To: FFmpeg development discussions and patches
Quoting Paul B Mahol (2023-09-28 11:48:14)
> On 9/28/23, Anton Khirnov <anton@khirnov.net> wrote:
> > Quoting Paul B Mahol (2023-09-27 21:53:54)
> >> Attached.
> >>
> >> From 6b7e51e2b4facead9c45fb94647c85b58e6fdf22 Mon Sep 17 00:00:00 2001
> >> From: Paul B Mahol <onemda@gmail.com>
> >> Date: Wed, 27 Sep 2023 21:48:49 +0200
> >> Subject: [PATCH] avcodec/photocd: allow decoding vlc with errors
> >>
> >> Also rename option that no longer works.
> >> Also make tables finding more robust.
> >
> > Why do all these things in a single patch?
> >
>
> I can boost my commits if you prefer that way.
Feel welcome.
> >> + s->streampos = (AV_RB16(avpkt->data + 2048 + 1536 + 3) + 12)
> >> * 2048;
> >
> > Where do these magic numbers come from? Same below.
>
> From offset from internal image file bitstream table structure.
Please describe that in a comment above that line then.
--
Anton Khirnov
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-09-27 19:53 [FFmpeg-devel] [PATCH] avcodec/photocd: allow decoding vlc with errors Paul B Mahol
2023-09-28 9:37 ` Anton Khirnov
2023-09-28 9:48 ` Paul B Mahol
2023-09-28 10:00 ` Anton Khirnov
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