diff mbox

[FFmpeg-devel,aacdec] Parse and drop gain control data, so that SSR packets decode.

Message ID CAPUDrwctOcPebP5JEDtXPWXx2stdzUAcFEG=oUvj6pm4CR9RTQ@mail.gmail.com
State New
Headers show

Commit Message

Dale Curtis Feb. 21, 2018, 12:56 a.m. UTC 
On Tue, Feb 20, 2018 at 4:18 PM, Alex Converse <alex.converse@gmail.com>
wrote:

>
> I would make this uint8_t
>

Done.


> I would drop this stack struck and replace the leaf get_bits() with
> skip bits. It makes the code that much harder to exploit and there is
> no point in storing data we don't plan on decoding
>

Done.


> This block seems funny. decode_gain_control() always returns zero.
> Maybe make this warn once per stream when present like some of the
> other AAC warn
> cases.
>

Done. I've added an AACContext::warn_gain_control member to do this.

This patch set also changes the attribution from Robert Swain to Maxim
Gavrilov based on svn blame of the SoC repository after discussion at
https://trac.ffmpeg.org/ticket/1693#comment:34

Comments

Alex Converse Feb. 21, 2018, 3:56 a.m. UTC | #1 
On Tue, Feb 20, 2018 at 4:56 PM, Dale Curtis <dalecurtis@chromium.org> wrote:
> On Tue, Feb 20, 2018 at 4:18 PM, Alex Converse <alex.converse@gmail.com>
> wrote:
>
>>
>> I would make this uint8_t
>>
>
> Done.
>
>
>> I would drop this stack struck and replace the leaf get_bits() with
>> skip bits. It makes the code that much harder to exploit and there is
>> no point in storing data we don't plan on decoding
>>
>
> Done.
>
>
>> This block seems funny. decode_gain_control() always returns zero.
>> Maybe make this warn once per stream when present like some of the
>> other AAC warn
>> cases.
>>
>
> Done. I've added an AACContext::warn_gain_control member to do this.
>
> This patch set also changes the attribution from Robert Swain to Maxim
> Gavrilov based on svn blame of the SoC repository after discussion at
> https://trac.ffmpeg.org/ticket/1693#comment:34
>

LGTM
diff mbox

Patch

From 8e5a3cc04400a1186df0714524ccb24dbe3f627d Mon Sep 17 00:00:00 2001
From: Dale Curtis <dalecurtis@chromium.org>
Date: Thu, 15 Feb 2018 16:22:55 -0800
Subject: [PATCH] [aacdec] Parse and drop gain control data, so that SSR
 packets decode.

This will result in poor quality audio for SSR streams, but they
will at least demux and decode without error; partially fixing
ticket #1693.

This pulls in the decode_gain_control() function from the
ffmpeg summer-of-code repo (original author Maxim Gavrilov) at
svn://svn.mplayerhq.hu/soc/aac/aac.c with some minor modifications
and adds AOT_AAC_SSR to decode_audio_specific_config_gb().

Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
Co-authored-by: Maxim Gavrilov <maxim.gavrilov@gmail.com>
---
 libavcodec/aac.h             |  2 ++
 libavcodec/aacdec_template.c | 36 +++++++++++++++++++++++++++++++++---
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/libavcodec/aac.h b/libavcodec/aac.h
index 4910c661d6..05bc95385f 100644
--- a/libavcodec/aac.h
+++ b/libavcodec/aac.h
@@ -357,6 +357,8 @@  struct AACContext {
     int warned_num_aac_frames;
     int warned_960_sbr;
 
+    int warned_gain_control;
+
     /* aacdec functions pointers */
     void (*imdct_and_windowing)(AACContext *ac, SingleChannelElement *sce);
     void (*apply_ltp)(AACContext *ac, SingleChannelElement *sce);
diff --git a/libavcodec/aacdec_template.c b/libavcodec/aacdec_template.c
index c2d9802023..cf97181092 100644
--- a/libavcodec/aacdec_template.c
+++ b/libavcodec/aacdec_template.c
@@ -997,6 +997,7 @@  static int decode_audio_specific_config_gb(AACContext *ac,
     switch (m4ac->object_type) {
     case AOT_AAC_MAIN:
     case AOT_AAC_LC:
+    case AOT_AAC_SSR:
     case AOT_AAC_LTP:
     case AOT_ER_AAC_LC:
     case AOT_ER_AAC_LD:
@@ -1967,6 +1968,33 @@  static void apply_prediction(AACContext *ac, SingleChannelElement *sce)
         reset_all_predictors(sce->predictor_state);
 }
 
+static void decode_gain_control(SingleChannelElement * sce, GetBitContext * gb)
+{
+    // wd_num, wd_test, aloc_size
+    static const uint8_t gain_mode[4][3] = {
+        {1, 0, 5},  // ONLY_LONG_SEQUENCE = 0,
+        {2, 1, 2},  // LONG_START_SEQUENCE,
+        {8, 0, 2},  // EIGHT_SHORT_SEQUENCE,
+        {2, 1, 5},  // LONG_STOP_SEQUENCE
+    };
+
+    const int mode = sce->ics.window_sequence[0];
+    uint8_t bd, wd, ad;
+
+    // FIXME: Store the gain control data on |sce| and do something with it.
+    uint8_t max_band = get_bits(gb, 2);
+    for (bd = 0; bd < max_band; bd++) {
+        for (wd = 0; wd < gain_mode[mode][0]; wd++) {
+            uint8_t adjust_num = get_bits(gb, 3);
+            for (ad = 0; ad < adjust_num; ad++) {
+                skip_bits(gb, 4 + ((wd == 0 && gain_mode[mode][1])
+                                     ? 4
+                                     : gain_mode[mode][2]));
+            }
+        }
+    }
+}
+
 /**
  * Decode an individual_channel_stream payload; reference: table 4.44.
  *
@@ -2034,9 +2062,11 @@  static int decode_ics(AACContext *ac, SingleChannelElement *sce,
                 goto fail;
         }
         if (!eld_syntax && get_bits1(gb)) {
-            avpriv_request_sample(ac->avctx, "SSR");
-            ret = AVERROR_PATCHWELCOME;
-            goto fail;
+            decode_gain_control(sce, gb);
+            if (!ac->warned_gain_control) {
+                avpriv_report_missing_feature(ac->avctx, "Gain control");
+                ac->warned_gain_control = 1;
+            }
         }
         // I see no textual basis in the spec for this occurring after SSR gain
         // control, but this is what both reference and real implmentations do
-- 
2.16.1.291.g4437f3f132-goog