Add seek support to transcode

src/transcode.c

@@ -245,6 +245,81 @@ transcode(struct transcode_ctx *ctx, struct evbuffer *evbuf, int wanted)
   return processed;
 }
 
+int
+transcode_seek(struct transcode_ctx *ctx, int ms)
+{
+  int64_t start_time;
+  int64_t target_pts;
+  int64_t got_pts;
+  int got_ms;
+  int flags;
+  int ret;
+
+  target_pts = ms * AV_TIME_BASE / 1000;
+  target_pts = av_rescale_q(target_pts, AV_TIME_BASE_Q, ctx->fmtctx->streams[ctx->astream]->time_base);
+
+  start_time = ctx->fmtctx->streams[ctx->astream]->start_time;
+
+  if ((start_time != AV_NOPTS_VALUE) && (start_time > 0))
+    target_pts += start_time;
+
+  ret = av_seek_frame(ctx->fmtctx, ctx->astream, target_pts, AVSEEK_FLAG_BACKWARD);
+  if (ret < 0)
+    {
+      DPRINTF(E_WARN, L_XCODE, "Could not seek into stream: %s\n", strerror(AVUNERROR(ret)));
+
+      return -1;
+    }
+
+  avcodec_flush_buffers(ctx->acodec);
+
+  ctx->acodec->hurry_up = 1;
+  flags = 0;
+  while (1)
+    {
+      if (ctx->apacket.data)
+	av_free_packet(&ctx->apacket);
+
+      ret = av_read_frame(ctx->fmtctx, &ctx->apacket);
+      if (ret < 0)
+	{
+	  DPRINTF(E_WARN, L_XCODE, "Could not read more data while seeking\n");
+
+	  flags = 1;
+	  break;
+	}
+
+      if (ctx->apacket.stream_index != ctx->astream)
+	continue;
+
+      /* Need a pts to return the real position */
+      if (ctx->apacket.pts == AV_NOPTS_VALUE)
+	continue;
+
+      break;
+    }
+
+  /* Error while reading frame above */
+  if (flags)
+    return -1;
+
+  /* Copy apacket data & size and do not mess with them */
+  ctx->apacket_data = ctx->apacket.data;
+  ctx->apacket_size = ctx->apacket.size;
+
+  /* Compute position in ms from pts */
+  if ((start_time != AV_NOPTS_VALUE) && (start_time > 0))
+    got_pts -= start_time;
+
+  got_pts = av_rescale_q(ctx->apacket.pts, ctx->fmtctx->streams[ctx->astream]->time_base, AV_TIME_BASE_Q);
+  got_ms = got_pts / (AV_TIME_BASE / 1000);
+
+  DPRINTF(E_DBG, L_XCODE, "Seek wanted %d ms, got %d ms\n", ms, got_ms);
+
+  return got_ms;
+}
+
+
 struct transcode_ctx *
 transcode_setup(struct media_file_info *mfi, off_t *est_size, int wavhdr)
 {

src/transcode.h

@@ -9,6 +9,9 @@ struct transcode_ctx;
 int
 transcode(struct transcode_ctx *ctx, struct evbuffer *evbuf, int wanted);
 
+int
+transcode_seek(struct transcode_ctx *ctx, int ms);
+
 struct transcode_ctx *
 transcode_setup(struct media_file_info *mfi, off_t *est_size, int wavhdr);