[FFmpeg-devel] avformat/mpeg: fix detection and demuxing of raw AC3 in mpegps

Submitted by Paul B Mahol on March 30, 2018, 4:46 p.m.

Details

Message ID 20180330164606.29914-1-onemda@gmail.com
State New
Headers show

Commit Message

Paul B Mahol March 30, 2018, 4:46 p.m.
Fixes #4889.

Signed-off-by: Paul B Mahol <onemda@gmail.com>
---
 libavformat/mpeg.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

Comments

Michael Niedermayer April 1, 2018, 2:35 p.m.
On Fri, Mar 30, 2018 at 06:46:06PM +0200, Paul B Mahol wrote:
> Fixes #4889.
> 
> Signed-off-by: Paul B Mahol <onemda@gmail.com>
> ---
>  libavformat/mpeg.c | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/libavformat/mpeg.c b/libavformat/mpeg.c
> index 69d4a9d8ac..f6e3439e68 100644
> --- a/libavformat/mpeg.c
> +++ b/libavformat/mpeg.c
> @@ -128,6 +128,7 @@ typedef struct MpegDemuxContext {
>      int sofdec;
>      int dvd;
>      int imkh_cctv;
> +    int raw_ac3;
>  #if CONFIG_VOBSUB_DEMUXER
>      AVFormatContext *sub_ctx;
>      FFDemuxSubtitlesQueue q[32];
> @@ -443,7 +444,15 @@ redo:
>  
>      if (startcode == PRIVATE_STREAM_1) {
>          startcode = avio_r8(s->pb);
> -        len--;
> +        if (avio_r8(s->pb) == 0x77 && startcode == 0x0b) {
> +            startcode = 0x80;
> +            m->raw_ac3 = 1;
> +            avio_skip(s->pb, -2);
> +        } else {
> +            m->raw_ac3 = 0;
> +            avio_skip(s->pb, -1);

I think these seekbacks are not safe, they could fail once every few thousand
times depending on buffer positions if the underlaying input is not seekable

a ffio_ensure_seekback() call should avoid this

thats unless iam missing something ...

[...]

thx

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diff --git a/libavformat/mpeg.c b/libavformat/mpeg.c
index 69d4a9d8ac..f6e3439e68 100644
--- a/libavformat/mpeg.c
+++ b/libavformat/mpeg.c
@@ -128,6 +128,7 @@  typedef struct MpegDemuxContext {
     int sofdec;
     int dvd;
     int imkh_cctv;
+    int raw_ac3;
 #if CONFIG_VOBSUB_DEMUXER
     AVFormatContext *sub_ctx;
     FFDemuxSubtitlesQueue q[32];
@@ -443,7 +444,15 @@  redo:
 
     if (startcode == PRIVATE_STREAM_1) {
         startcode = avio_r8(s->pb);
-        len--;
+        if (avio_r8(s->pb) == 0x77 && startcode == 0x0b) {
+            startcode = 0x80;
+            m->raw_ac3 = 1;
+            avio_skip(s->pb, -2);
+        } else {
+            m->raw_ac3 = 0;
+            avio_skip(s->pb, -1);
+            len--;
+        }
     }
     if (len < 0)
         goto error_redo;
@@ -486,14 +495,16 @@  redo:
         if (len < 4)
             goto skip;
 
-        /* audio: skip header */
-        avio_r8(s->pb);
-        lpcm_header_len = avio_rb16(s->pb);
-        len -= 3;
-        if (startcode >= 0xb0 && startcode <= 0xbf) {
-            /* MLP/TrueHD audio has a 4-byte header */
+        if (!m->raw_ac3) {
+            /* audio: skip header */
             avio_r8(s->pb);
-            len--;
+            lpcm_header_len = avio_rb16(s->pb);
+            len -= 3;
+            if (startcode >= 0xb0 && startcode <= 0xbf) {
+                /* MLP/TrueHD audio has a 4-byte header */
+                avio_r8(s->pb);
+                len--;
+            }
         }
     }